Resist composition, method of forming resist pattern, polymeric compound, and compound

ABSTRACT

A resist composition including a resin component having a structural unit derived from a compound represented by formula (a0-1), in which W represents a polymerizable group-containing group; Ra 01  represents an alkyl group or an aromatic heterocyclic group containing an oxygen atom or a sulfur atom; in the case where Ra 01  is an aromatic heterocyclic group containing an oxygen atom or a sulfur atom, Ra 02  is a group which forms an aliphatic cyclic group containing an electron-withdrawing group, together with the tertiary carbon atom (*C) to which Ra 01  is bonded; and when Ra 01  is an alkyl group, Ra 02  is a group in which an aliphatic cyclic group containing an electron-withdrawing group forms a condensed ring together with an aromatic heterocyclic group containing an oxygen atom or a sulfur atom.

TECHNICAL FIELD

The present invention relates to a resist composition, a method offorming a resist pattern, a polymeric compound, and a compound.

Priority is claimed on Japanese Patent Application No. 2017-195388,filed Oct. 5, 2017, the content of which is incorporated herein byreference.

DESCRIPTION OF RELATED ART

In lithography techniques, for example, a resist film composed of aresist material is formed on a substrate, and the resist film issubjected to selective exposure, followed by development, therebyforming a resist pattern having a predetermined shape on the resistfilm. A resist material in which the exposed portions of the resist filmbecome soluble in a developing solution is called a positive-type, and aresist material in which the exposed portions of the resist film becomeinsoluble in a developing solution is called a negative-type.

In recent years, in the production of semiconductor elements and liquidcrystal display elements, advances in lithography techniques have led torapid progress in the field of pattern miniaturization. Typically, theseminiaturization techniques involve shortening the wavelength (increasingthe energy) of the exposure light source. Conventionally, ultravioletradiation typified by g-line and i-line radiation has been used, butnowadays KrF excimer lasers and ArF excimer lasers are used in massproduction. Furthermore, research is also being conducted intolithography techniques that use an exposure light source having awavelength shorter (energy higher) than these excimer lasers, such aselectron beam (EB), extreme ultraviolet radiation (EUV), and X ray.

Resist materials for use with these types of exposure light sourcesrequire lithography properties such as a high resolution capable ofreproducing patterns of minute dimensions, and a high level ofsensitivity to these types of exposure light sources.

As a resist material that satisfies these conditions, a chemicallyamplified composition is used, which includes a base material componentthat exhibits a changed solubility in a developing solution under theaction of acid and an acid-generator component that generates acid uponexposure.

For example, in the case where the developing solution is an alkalideveloping solution (alkali developing process), a chemically amplifiedpositive resist which contains, as a base component (base resin), aresin which exhibits increased solubility in an alkali developingsolution under action of acid, and an acid generator is typically used.If a resist film formed using such a resist composition is selectivelyexposed at the time of forming a resist pattern, in exposed areas, acidis generated from the acid generator component, and the polarity of thebase resin increases by the action of the generated acid, thereby makingthe exposed areas of the resist film soluble in the alkali developingsolution. Thus, by alkali developing, the exposed portions of the resistfilm are dissolved and removed, whereas the unexposed portions of theresist film remain as patterns, thereby forming a positive resistpattern.

On the other hand, when such a base resin is applied to a solventdeveloping process using a developing solution containing an organicsolvent (organic developing solution), the solubility of the exposedportions in an organic developing solution is decreased. As a result,the unexposed portions of the resist film are dissolved and removed bythe organic developing solution, and a negative resist pattern in whichthe exposed portions of the resist film are remaining is formed. Such asolvent developing process for forming a negative-tone resistcomposition is sometimes referred to as “negative-tone developingprocess”.

In general, the base resin used for a chemically amplified resistcomposition contains a plurality of structural units for improvinglithography properties and the like.

For example, in the case of a resin composition which exhibits increasedsolubility in an alkali developing solution by the action of acid, astructural unit containing an acid decomposable group which isdecomposed by the action of acid generated from an acid generatorcomponent and exhibits increased polarity. Further, a structural unitcontaining a lactone-containing cyclic group or a structural unitcontaining a polar group such as a hydroxy group is used in combination.

As the acid-generator component used in a chemically amplified resistcomposition, various kinds have been proposed. For example, onium saltacid generators such as iodonium salts and sulfonium salts; oximesulfonate acid generators; diazomethane acid generators;nitrobenzylsulfonate acid generators; iminosulfonate acid generators;and disulfone acid generators are known.

As onium salt acid generators, those which have an onium ion such astriphenylsulfonium in the cation moiety are mainly used. Generally, asthe anion moiety for onium salt acid generators, an alkylsulfonate ionor a fluorinated alkylsulfonate ion in which part or all of the hydrogenatoms within the aforementioned alkylsulfonate ion has been substitutedwith fluorine atoms is typically used.

In the formation of a resist pattern, the behavior of acid generatedfrom the acid-generator component upon exposure is one of the factorswhich has large influence on the lithography properties.

In particular, when a resist film is exposed with EUV (extremeultraviolet) or EB (electron beam), in the resist material, control ofacid diffusion becomes a problem. Conventionally, for controlling aciddiffusion, various methods of changing the design of the base resin hasbeen proposed.

For example, there has been proposed a resist composition in which apolymer having a specific acid dissociable group containing an arylgroup is employed to improve sensitivity and resolution (see, forexample, Patent Literature 1).

DOCUMENTS OF RELATED ART Patent Literature

-   [Patent Literature 1] WO2011/040175

SUMMARY OF THE INVENTION

As the lithography technique further progresses and the miniaturizationof the resist pattern progresses more and more, for example, a target ofthe lithography performed by electron beams and EUV is to form fineresist patterns of several tens of nanometers. As miniaturization ofresist pattern progress, resist composition is demanded to exhibitimproved sensitivity to the exposure source and good lithographyproperties (resolution, reduced roughness, and the like).

However, in a conventional resist composition, when it is attempted toimprove sensitivity to an exposure source such as EUV, it becomesdifficult to obtain a resist pattern having a desired shape. Therefore,it was difficult to satisfy both the sensitivity and the pattern shape.

The present invention takes the above circumstances into consideration,with an object of providing a polymeric compound useful as a basecomponent of a resist composition, a compound which is a monomer of thepolymeric compound, a resist composition containing the polymericcompound, and a method of forming a resist pattern using the resistcomposition.

For solving the above-mentioned problems, the present invention employsthe following aspects.

Specifically, a first aspect of the present invention is a resistcomposition which generates acid upon exposure and exhibits changedsolubility in a developing solution under action of acid, the resistcomposition including a resin component (A1) which exhibits changedsolubility in a developing solution under action of acid, the resincomponent (A1) including a structural unit (a0) derived from a compoundrepresented by general formula (a0-1) shown below.

In the formula, W represents a polymerizable group-containing group;Ra⁰¹ represents an alkyl group or an aromatic heterocyclic groupcontaining an oxygen atom or a sulfur atom; in the case where Ra⁰¹ is anaromatic heterocyclic group containing an oxygen atom or a sulfur atom,Ra⁰² is a group which forms an aliphatic cyclic group together with thetertiary carbon atom (*C) to which Ra⁰¹ is bonded, provided that thealiphatic cyclic group contains an electron-withdrawing group as asubstituent; and in the case where Ra⁰¹ is an alkyl group, Ra⁰² is agroup in which an aliphatic cyclic group forms a condensed ring togetherwith an aromatic heterocyclic group containing an oxygen atom or asulfur atom, provided that the aliphatic cyclic group is formed togetherwith the tertiary carbon atom (*C) to which Ra⁰¹ is bonded, and thealiphatic cyclic group contains an electron-withdrawing group as asubstituent.

A second aspect of the present invention is a method of forming a resistpattern, including: using a resist composition according to the firstaspect to form a resist film, exposing the resist film, and developingthe exposed resist film to form a resist pattern.

A third aspect of the present invention is a polymeric compoundincluding a structural unit (a0) derived from a compound represented bythe aforementioned general formula (a0-1).

A fourth aspect of the present invention is a compound represented bythe aforementioned general formula (a0-1).

According to the present invention, there are provided a polymericcompound useful as a base component of a resist composition, a compoundwhich is a monomer of the polymeric compound, a resist compositioncontaining the polymeric compound, and a method of forming a resistpattern using the resist composition.

According to the resist composition of the present invention,sensitivity can be improved in the formation of a resist pattern, and itbecomes possible to form a resist pattern exhibiting good lithographyproperties (resolution, reduced roughness, and the like).

DETAILED DESCRIPTION OF THE INVENTION

In the present description and claims, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound that has no aromaticity.

The term “alkyl group” includes linear, branched or cyclic, monovalentsaturated hydrocarbon, unless otherwise specified. The same applies forthe alkyl group within an alkoxy group.

The term “alkylene group” includes linear, branched or cyclic, divalentsaturated hydrocarbon, unless otherwise specified.

A “halogenated alkyl group” is a group in which part or all of thehydrogen atoms of an alkyl group is substituted with a halogen atom.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

A “fluorinated alkyl group” or a “fluorinated alkylene group” is a groupin which part or all of the hydrogen atoms of an alkyl group or analkylene group have been substituted with a fluorine atom.

The term “structural unit” refers to a monomer unit that contributes tothe formation of a polymeric compound (resin, polymer, copolymer).

The expression “may have a substituent” means that a case where ahydrogen atom (—H) is substituted with a monovalent group, or a casewhere a methylene (—CH₂—) group is substituted with a divalent group.

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

A “structural unit derived from an acrylate ester” refers to astructural unit that is formed by the cleavage of the ethylenic doublebond of an acrylate ester.

An “acrylate ester” refers to a compound in which the terminal hydrogenatom of the carboxy group of acrylic acid (CH₂═CH—COOH) has beensubstituted with an organic group.

The acrylate ester may have the hydrogen atom bonded to the carbon atomon the α-position substituted with a substituent. The substituent(R^(α0)) that substitutes the hydrogen atom bonded to the carbon atom onthe α-position is an atom other than hydrogen or a group, and examplesthereof include an alkyl group of 1 to 5 carbon atoms and a halogenatedalkyl group of 1 to 5 carbon atoms. Further, an acrylate ester havingthe hydrogen atom bonded to the carbon atom on the α-positionsubstituted with a substituent (R^(α0)) in which the substituent hasbeen substituted with a substituent containing an ester bond (e.g., anitaconic acid diester), or an acrylic acid having the hydrogen atombonded to the carbon atom on the α-position substituted with asubstituent (R^(α0)) in which the substituent has been substituted witha hydroxyalkyl group or a group in which the hydroxy group within ahydroxyalkyl group has been modified (e.g., α-hydroxyalkyl acrylateester) can be mentioned as an acrylate ester having the hydrogen atombonded to the carbon atom on the α-position substituted with asubstituent. A carbon atom on the α-position of an acrylate ester refersto the carbon atom bonded to the carbonyl group, unless specifiedotherwise.

Hereafter, an acrylate ester having the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent issometimes referred to as “α-substituted acrylate ester”. Further,acrylate esters and α-substituted acrylate esters are collectivelyreferred to as “(α-substituted) acrylate ester”. Hereafter, an acrylateester having the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent is sometimes referred to as“α-substituted acrylate ester”. Further, acrylic acid and α-substitutedacrylic acids are collectively referred to as “(α-substituted) acrylicacid”.

A “structural unit derived from acrylaminde” refers to a structural unitthat is formed by the cleavage of the ethylenic double bond ofacrylaminde.

The acrylamide may have the hydrogen atom bonded to the carbon atom onthe α-position substituted with a substituent, and may have either orboth terminal hydrogen atoms on the amino group of acrylamidesubstituted with a substituent. A carbon atom on the α-position of anacrylamide refers to the carbon atom bonded to the carbonyl group,unless specified otherwise.

As the substituent which substitutes the hydrogen atom on the α-positionof acrylamide, the same substituents as those described above for thesubstituent (R^(α0)) on the α-position of the aforementioned α-positionof the aforementioned α-substituted acrylate ester can be mentioned.

A “structural unit derived from hydroxystyrene” refers to a structuralunit that is formed by the cleavage of the ethylenic double bond ofhydroxystyrene. A “structural unit derived from a hydroxystyrenederivative” refers to a structural unit that is formed by the cleavageof the ethylenic double bond of a hydroxystyrene derivative.

The term “hydroxystyrene derivative” includes compounds in which thehydrogen atom at the α-position of hydroxystyrene has been substitutedwith another substituent such as an alkyl group or a halogenated alkylgroup; and derivatives thereof. Examples of the derivatives thereofinclude hydroxystyrene in which the hydrogen atom of the hydroxy grouphas been substituted with an organic group and may have the hydrogenatom on the α-position substituted with a substituent; andhydroxystyrene which has a substituent other than a hydroxy group bondedto the benzene ring and may have the hydrogen atom on the α-positionsubstituted with a substituent. Here, the α-position (carbon atom on theα-position) refers to the carbon atom having the benzene ring bondedthereto, unless specified otherwise.

As the substituent which substitutes the hydrogen atom on the α-positionof hydroxystyrene, the same substituents as those described above forthe substituent on the α-position of the aforementioned α-substitutedacrylate ester can be mentioned.

A “structural unit derived from vinylbenzoic acid or a vinylbenzoic acidderivative” refers to a structural unit that is formed by the cleavageof the ethylenic double bond of vinylbenzoic acid or a vinylbenzoic acidderivative.

The term “vinylbenzoic acid derivative” includes compounds in which thehydrogen atom at the α-position of vinylbenzoic acid has beensubstituted with another substituent such as an alkyl group or ahalogenated alkyl group; and derivatives thereof. Examples of thederivatives thereof include benzoic acid in which the hydrogen atom ofthe carboxy group has been substituted with an organic group and mayhave the hydrogen atom on the α-position substituted with a substituent;and benzoic acid which has a substituent other than a hydroxy group anda carboxy group bonded to the benzene ring and may have the hydrogenatom on the α-position substituted with a substituent. Here, theα-position (carbon atom on the α-position) refers to the carbon atomhaving the benzene ring bonded thereto, unless specified otherwise.

As the alkyl group as a substituent on the α-position, a linear orbranched alkyl group is preferable, and specific examples include alkylgroups of 1 to 5 carbon atoms, such as a methyl group, an ethyl group, apropyl group, an isopropyl group, an n-butyl group, an isobutyl group, atert-butyl group, a pentyl group, an isopentyl group and a neopentylgroup.

Specific examples of the halogenated alkyl group as the substituent onthe α-position include groups in which part or all of the hydrogen atomsof the aforementioned “alkyl group as the substituent on the α-position”are substituted with halogen atoms. Examples of the halogen atom includea fluorine atom, a chlorine atom, a bromine atom and an iodine atom, anda fluorine atom is particularly desirable.

Specific examples of the hydroxyalkyl group as the substituent on theα-position include groups in which part or all of the hydrogen atoms ofthe aforementioned “alkyl group as the substituent on the α-position”are substituted with a hydroxy group. The number of hydroxy groupswithin the hydroxyalkyl group is preferably 1 to 5, and most preferably1.

In the present specification and claims, some structures represented bychemical formulae may have an asymmetric carbon, such that an enantiomeror a diastereomer may be present. In such a case, the one formularepresents all isomers. The isomers may be used individually, or in theform of a mixture.

(Resist Composition)

The resist composition of the present embodiment generates acid uponexposure and exhibits changed solubility in a developing solution underaction of acid.

The resist composition contains a base component (A) (hereafter,sometimes referred to as “base component (A)”) which exhibits changedsolubility in a developing solution.

When a resist film is formed using the resist composition according tothe present embodiment, and the resist film is selectively exposed, acidis generated at exposed portions of the resist film, and the solubilityof the component (A) in a developing solution is changed by the actionof the acid. On the other hand, at unexposed portions of the resistfilm, the solubility of the component (A) in a developing solution isunchanged. As a result, difference is generated between the exposedportions of the resist film and the unexposed portions of the resistfilm in terms of solubility in a developing solution. Therefore, bysubjecting the resist film to development, the exposed portions of theresist film are dissolved and removed to form a positive-tone resistpattern in the case of a positive resist, whereas the unexposed portionsof the resist film are dissolved and removed to form a negative-toneresist pattern in the case of a negative resist.

In the present specification, a resist composition which forms apositive resist pattern by dissolving and removing the exposed portionsof the resist film is called a positive resist composition, and a resistcomposition which forms a negative resist pattern by dissolving andremoving the unexposed portions of the resist film is called a negativeresist composition.

The resist composition of the present embodiment may be either apositive resist composition or a negative resist composition.

Further, in the present embodiment, the resist composition may beapplied to an alkali developing process using an alkali developingsolution in the developing treatment, or a solvent developing processusing a developing solution containing an organic solvent (organicdeveloping solution) in the developing treatment, and preferably asolvent developing process.

That is, the resist composition of the present embodiment is preferablya resist composition which forms a positive pattern in an alkalideveloping process (i.e, a positive resist compound for alkalideveloping process) or a resist composition which forms a negativepattern in a solvent developing process (i.e., a negative type resistcomposition for solvent developing process).

The resist composition of the present embodiment is capable ofgenerating acid upon exposure. The acid may be generated from thecomponent (A) upon exposure, or the acid may be generated from anadditive component other than the component (A) upon exposure.

In the present embodiment, the resist composition may be a resistcomposition (1) containing an acid generator component (B) whichgenerates acid upon exposure (hereafter, referred to as “component (B)”;a resist composition (2) in which the component (A) is a component whichgenerates acid upon exposure; or a resist composition (3) in which thecomponent (A) is a component which generates acid upon exposure, andfurther containing an acid generator component (B).

That is, when the resist composition of the present invention is theaforementioned resist composition (2) or (3), the component (A) is a“base component which generates acid upon exposure and exhibits changedsolubility in a developing solution under action of acid”. In the casewhere the component (A) is a base component which generates acid uponexposure and exhibits changed solubility in a developing solution underaction of acid, the component (A1) described later is preferably apolymeric compound which generates acid upon exposure and exhibitschanged solubility in a developing solution under action of acid. As thepolymeric compound, a resin having a structural unit which generatesacid upon exposure may be used.

As the structural unit which generates acid upon exposure, aconventional structural unit may be used.

The resist composition of the present embodiment is most preferably theaforementioned resist composition (1).

<Component (A)>

The component (A) is a base component which exhibits changed solubilityin a developing solution under action of acid.

In the present invention, the term “base component” refers to an organiccompound capable of forming a film, and is preferably an organiccompound having a molecular weight of 500 or more. When the organiccompound has a molecular weight of 500 or more, the film-forming abilityis improved, and a resist pattern of nano level can be easily formed.

The organic compound used as the base component is broadly classifiedinto non-polymers and polymers.

In general, as a non-polymer, any of those which have a molecular weightin the range of 500 to less than 4,000 is used. Hereafter, a “lowmolecular weight compound” refers to a non-polymer having a molecularweight in the range of 500 to less than 4,000.

As a polymer, any of those which have a molecular weight of 1,000 ormore is generally used. Hereafter, a “resin” or a “polymer” refers to apolymer having a molecular weight of 1,000 or more.

As the molecular weight of the polymer, the weight average molecularweight in terms of the polystyrene equivalent value determined by gelpermeation chromatography (GPC) is used.

In the resist composition according to the present embodiment, thecomponent (A) contains a resin component (A1) (hereafter, referred to as“component (A1)”) which exhibits changed solubility in a developingsolution by the action of acid.

As the component (A), at least the component (A1) is used, and apolymeric compound and/or a low molecular weight compound may be used incombination with the component (A1).

<<Component (A1)>>

The component (A1) includes a structural unit (a0) derived from acompound represented by general formula (a0-1) described later. Ifdesired, the component (A1) may include, in addition to the structuralunit (a0), other structural unit.

In the resist composition of the present embodiment, since thestructural unit (a0) contains an acid dissociable group, by using thecomponent (A1), the polarity of the resin component changes before andafter exposure. Therefore, an excellent development contrast can beobtained between exposed portions and unexposed portions of the resistfilm not only in an alkali developing process, but also in a solventdeveloping process.

More specifically, in the case of applying an alkali developing process,the component (A1) is substantially insoluble in an alkali developingsolution prior to exposure, but when acid is generated from thecomponent (B) upon exposure, the action of this acid causes an increasein the polarity of the base component, thereby increasing the solubilityof the component (A1) in an alkali developing solution. Therefore, inthe formation of a resist pattern, by conducting selective exposure of aresist film formed by applying the resist composition to a substrate,the exposed portions of the resist film change from an insoluble stateto a soluble state in an alkali developing solution, whereas theunexposed portions of the resist film remain insoluble in an alkalideveloping solution, and hence, a positive resist pattern is formed byalkali developing.

On the other hand, in the case of a solvent developing process, thecomponent (A1) exhibits high solubility in an organic developingsolution prior to exposure, and when acid is generated from thecomponent (B) upon exposure for example, the polarity of the component(A1) is increased by the action of the generated acid, therebydecreasing the solubility of the component (A1) in an organic developingsolution. Therefore, in the formation of a resist pattern, by conductingselective exposure of a resist film formed by applying the resistcomposition to a substrate, the exposed portions of the resist filmchanges from an soluble state to an insoluble state in an organicdeveloping solution, whereas the unexposed portions of the resist filmremain soluble in an organic developing solution. As a result, byconducting development using an organic developing solution, therebyforming a negative resist pattern.

Structural Unit (a0):

The structural unit (a0) is a structural unit derived from a compoundrepresented by general formula (a0-1) shown below (compound (a0)). Inthe structural unit (a0), the tertiary carbon atom-containing group informula (a0-1) is an acid dissociable group, and protects the oxy group(—O—) side of the carbonyloxy group [—C(═O)—O—] in formula (a0-1). An“acid dissociable group” exhibits acid dissociability such that the bondbetween the acid dissociable group and the adjacent oxygen atom (O) iscleaved by the action of acid. When the acid dissociable group isdissociated by the action of acid, a polar group which exhibits a higherpolarity than the acid dissociable group is generated, and the polarityis increased. As a result, the polarity of the entire component (A1) isincreased. By the increase in the polarity, the solubility in an alkalideveloping solution changes, and the solubility in an alkali developingsolution is relatively increased, whereas the solubility in an organicdeveloping solution is relatively decreased.

In the formula, W represents a polymerizable group-containing group;Ra⁰¹ represents an alkyl group or an aromatic heterocyclic groupcontaining an oxygen atom or a sulfur atom; in the case where Ra⁰¹ is anaromatic heterocyclic group containing an oxygen atom or a sulfur atom,Ra⁰² is a group which forms an aliphatic cyclic group together with thetertiary carbon atom (*C) to which Ra⁰¹ is bonded, provided that thealiphatic cyclic group contains an electron-withdrawing group as asubstituent; and in the case where Ra⁰¹ is an alkyl group, Ra⁰² is agroup in which an aliphatic cyclic group forms a condensed ring togetherwith an aromatic heterocyclic group containing an oxygen atom or asulfur atom, provided that the aliphatic cyclic group is formed togetherwith the tertiary carbon atom (*C) to which Ra⁰¹ is bonded, and thealiphatic cyclic group contains an electron-withdrawing group as asubstituent.

In general formula (a0-1), W represents a polymerizable group-containinggroup.

The “polymerizable group” for W refers to a group that renders acompound containing the group polymerizable by a radical polymerizationor the like, for example, a group having a carbon-carbon multiple bondsuch as an ethylenic double bond.

Examples of the polymerizable group include a vinyl group, an allylgroup, an acryloyl group, a methacryloyl group, a fluorovinyl group, adifluorovinyl group, a trifluorovinyl group, adifluorotrifluoromethylvinyl group, a trifluoroallyl group, aperfluoroallyl group, a trifluoromethylacryloyl group, anonylfluorobutylacryloyl group, a vinyl ether group, afluorine-containing vinyl ether group, an allyl ether group, anfluorine-containing allyl ether group, a styryl group, a vinylnaphthylgroup, a fluorine-containing styryl group, a fluorine-containingvinylnaphthyl group, a norbornyl group, a fluorine-containing norbornylgroup, and a silyl group.

The polymerizable group-containing group may be a group constituted ofonly a polymerizable group, or a group constituted of a polymerizablegroup and a group other than a polymerizable group. Examples of thegroup other than a polymerizable group include a divalent hydrocarbongroup which may have a substituent, and a divalent linking groupcontaining a hetero atom.

Preferable example of W include a group represented by a chemicalformula: CH₂═C(R)—Ya^(x0)-. In the chemical formula, R represents ahydrogen atom, an alkyl group of 1 to 5 carbon atoms or a halogenatedalkyl group of 1 to 5 carbon atoms; and Ya^(x0) represents a single bondor a divalent linking group.

In the aforementioned chemical formula, as the alkyl group of 1 to 5carbon atoms for R, a linear or branched alkyl group of 1 to 5 carbonatoms is preferable, and specific examples thereof include a methylgroup, an ethyl group, a propyl group, an isopropyl group, an n-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group and a neopentyl group. The halogenated alkyl group of 1to 5 carbon atoms represented by R is a group in which part or all ofthe hydrogen atoms of the aforementioned alkyl group of 1 to 5 carbonatoms have been substituted with halogen atoms. Examples of the halogenatom include a fluorine atom, a chlorine atom, a bromine atom and aniodine atom, and a fluorine atom is particularly desirable. As R, ahydrogen atom, an alkyl group of 1 to 5 carbon atoms or a fluorinatedalkyl group of 1 to 5 carbon atoms is preferable, and in terms ofindustrial availability, a hydrogen atom or a methyl group is morepreferable, and a methyl group is still more preferable.

In the aforementioned chemical formula, the divalent linking group forYa^(x0) is not particularly limited, and preferable examples thereofinclude a divalent hydrocarbon group which may have a substituent and adivalent linking group containing a hetero atom.

Divalent Hydrocarbon Group which May have a Substituent:

In the case where Ya^(x0) is a divalent linking group which may have asubstituent, the hydrocarbon group may be either an aliphatichydrocarbon group or an aromatic hydrocarbon group.

Aliphatic Hydrocarbon Group for Ya^(x0)

An “aliphatic hydrocarbon group” refers to a hydrocarbon group that hasno aromaticity. The aliphatic hydrocarbon group may be saturated orunsaturated. In general, the aliphatic hydrocarbon group is preferablysaturated.

Examples of the aliphatic hydrocarbon group include a linear or branchedaliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

Linear or Branched Aliphatic Hydrocarbon Group

The linear aliphatic hydrocarbon group preferably has 1 to 10 carbonatoms, more preferably 1 to 6, still more preferably 1 to 4, and mostpreferably 1 to 3.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—] and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group preferably has 2 to 10 carbonatoms, more preferably 3 to 6, still more preferably 3 or 4, and mostpreferably 3.

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include a fluorine atom, afluorinated alkyl group of 1 to 5 carbon atoms, and a carbonyl group.

Aliphatic Hydrocarbon Group Containing a Ring in the Structure Thereof

As examples of the hydrocarbon group containing a ring in the structurethereof, a cyclic aliphatic hydrocarbon group containing a hetero atomin the ring structure thereof and may have a substituent (a group inwhich two hydrogen atoms have been removed from an aliphatic hydrocarbonring), a group in which the cyclic aliphatic hydrocarbon group is bondedto the terminal of the aforementioned chain-like aliphatic hydrocarbongroup, and a group in which the cyclic aliphatic group is interposedwithin the aforementioned linear or branched aliphatic hydrocarbongroup, can be given. As the linear or branched aliphatic hydrocarbongroup, the same groups as those described above can be used.

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbonatoms, and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be either a polycyclic groupor a monocyclic group. As the monocyclic aliphatic hydrocarbon group, agroup in which 2 hydrogen atoms have been removed from a monocycloalkaneis preferable. The monocycloalkane preferably has 3 to 6 carbon atoms,and specific examples thereof include cyclopentane and cyclohexane. Asthe polycyclic group, a group in which 2 hydrogen atoms have beenremoved from a polycycloalkane is preferable, and the polycyclic grouppreferably has 7 to 12 carbon atoms. Examples of the polycycloalkaneinclude adamantane, norbornane, isobornane, tricyclodecane andtetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup and a carbonyl group.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and more preferably a methyl group, an ethyl group, apropyl group, an n-butyl group or a tert-butyl group.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and still more preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned alkyl groups has been substituted with the aforementionedhalogen atoms.

The cyclic aliphatic hydrocarbon group may have part of the carbon atomsconstituting the ring structure thereof substituted with a substituentcontaining a hetero atom. As the substituent containing a hetero atom,—O—, —C(═O)—O—, —S—, —S(═O)₂— or —S(═O)₂—O— is preferable.

Aromatic Hydrocarbon Group for Ya^(x0)

The aromatic hydrocarbon group is a hydrocarbon group having at leastone aromatic ring.

The aromatic ring is not particularly limited, as long as it is a cyclicconjugated compound having (4n+2)π electrons, and may be eithermonocyclic or polycyclic. The aromatic ring preferably has 5 to 30carbon atoms, more preferably 5 to 20 carbon atoms, and still morepreferably 6 to 15 carbon atoms, and most preferably 6 to 12 carbonatoms. Here, the number of carbon atoms within a substituent(s) is notincluded in the number of carbon atoms of the aromatic hydrocarbongroup.

Examples of the aromatic ring include aromatic hydrocarbon rings, suchas benzene, naphthalene, anthracene and phenanthrene; and aromatichetero rings in which part of the carbon atoms constituting theaforementioned aromatic hydrocarbon rings has been substituted with ahetero atom. Examples of the hetero atom within the aromatic heterorings include an oxygen atom, a sulfur atom and a nitrogen atom.Specific examples of the aromatic hetero ring include a pyridine ringand a thiophene ring.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the aforementionedaromatic hydrocarbon ring or aromatic hetero ring (arylene group orheteroarylene group); a group in which two hydrogen atoms have beenremoved from an aromatic compound having two or more aromatic rings(biphenyl, fluorene or the like); and a group in which one hydrogen atomof the aforementioned aromatic hydrocarbon ring or aromatic hetero ringhas been substituted with an alkylene group (a group in which onehydrogen atom has been removed from the aryl group within theaforementioned arylalkyl group such as a benzyl group, a phenethylgroup, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a1-naphthylethyl group, or a 2-naphthylethyl group, or a heteroarylalkylgroup). The alkylene group which is bonded to the aforementioned arylgroup or heteroaryl group preferably has 1 to 4 carbon atoms, morepreferably 1 or 2 carbon atoms, and most preferably 1 carbon atom.

With respect to the aromatic hydrocarbon group, the hydrogen atom withinthe aromatic hydrocarbon group may be substituted with a substituent.For example, the hydrogen atom bonded to the aromatic ring within thearomatic hydrocarbon group may be substituted with a substituent.Examples of substituents include an alkyl group, an alkoxy group, ahalogen atom, a halogenated alkyl group, and a hydroxyl group.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and more preferably a methyl group, an ethyl group, apropyl group, an n-butyl group or a tert-butyl group.

As the alkoxy group, the halogen atom and the halogenated alkyl groupfor the substituent, the same groups as the aforementioned substituentgroups for substituting a hydrogen atom within the cyclic aliphatichydrocarbon group can be used.

Divalent Linking Group Containing a Hetero Atom

In the case where Ya^(x0) represents a divalent linking group containinga hetero atom, preferable examples of the linking group include —O—,—C(═O)—O—, —O—C(═O)—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH—,—NH—C(═NH)— (may be substituted with a substituent such as an alkylgroup, an acyl group or the like), —S—, —S(═O)₂—, —S(═O)₂—O—, and agroup represented by general formula: —Y²¹—O—Y²²—, —Y²¹—O—,—Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—, —[Y²¹—C(═O)—O]_(m″)—Y²²—,—Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²— [in the formulae, Y²¹ and Y²²each independently represents a divalent hydrocarbon group which mayhave a substituent, O represents an oxygen atom, and m′ represents aninteger of 0 to 3].

In the case where the divalent linking group containing a hetero atom is—C(═O)—NH—, —C(═O)—NH—C(═O)—, —NH— or —NH—C(═NH)—, H may be substitutedwith a substituent such as an alkyl group, an acyl group or the like.The substituent (an alkyl group, an acyl group or the like) preferablyhas 1 to 10 carbon atoms, more preferably 1 to 8, and most preferably 1to 5.

In general formulae —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—,—[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²—, Y²¹and Y²² each independently represents a divalent hydrocarbon group whichmay have a substituent. Examples of the divalent hydrocarbon groupinclude the same groups as those described above as the “divalenthydrocarbon group which may have a substituent” in the explanation ofthe aforementioned divalent linking group.

As Y²¹, a linear aliphatic hydrocarbon group is preferable, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, and a methylene group or anethylene group is particularly desirable.

As Y²², a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group or an alkylmethylene group ismore preferable. The alkyl group within the alkylmethylene group ispreferably a linear alkyl group of 1 to 5 carbon atoms, more preferablya linear alkyl group of 1 to 3 carbon atoms, and most preferably amethyl group.

In the group represented by the formula —[Y²¹—C(═O)—O]_(m)″—Y²²—, m″represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1. Namely, it is particularlydesirable that the group represented by the formula—[Y²¹—C(═O)—O]_(m)″—Y²²— is a group represented by the formula—Y²¹—C(═O)—O—Y²²—. Among these, a group represented by the formula—(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′ is aninteger of 1 to 10, preferably an integer of 1 to 8, more preferably aninteger of 1 to 5, still more preferably 1 or 2, and most preferably 1.b′ is an integer of 1 to 10, preferably an integer of 1 to 8, morepreferably an integer of 1 to 5, still more preferably 1 or 2, and mostpreferably 1.

Among these examples, as Ya^(x0), a single bond, an ester bond[—C(═O)—O—, —O—C(═O)—], an ether bond (—O—), a linear or branchedalkylene group, or a combination of any of these groups is preferable, asingle bond or an ester bond [—C(═O)—O—, —O—C(═O)—] is more preferable,and an ester bond [—C(═O)—O—] is still more preferable.

In formula (a0-1), Ra⁰¹ represents an alkyl group or an aromaticheterocyclic group containing an oxygen atom or a sulfur atom.

In formula (a0-1), in the case where Ra⁰¹ is an aromatic heterocyclicgroup containing an oxygen atom or a sulfur atom, the aromaticheterocyclic group is a group in which one hydrogen atom has beenremoved from an aromatic heterocyclic ring formed by substituting partof the carbon atoms constituting an aromatic hydrocarbon ringsubstituted with an oxygen atom or a sulfur atom.

The aromatic hydrocarbon ring is not particularly limited, as long as itis a cyclic conjugated compound having (4n+2)π electrons, and may beeither monocyclic or polycyclic. The aromatic hydrocarbon ringpreferably has 5 to 30 carbon atoms, more preferably 5 to 20 carbonatoms, and still more preferably 5 to 15 carbon atoms, and mostpreferably 5 to 12 carbon atoms.

The aromatic heterocyclic ring which constitutes the aromaticheterocyclic group for Ra⁰¹ has at least one of an oxygen atom and asulfur atom, and may also have a hetero atom other than oxygen andsulfur (such as a nitrogen atom).

Specific examples of the aromatic heterocyclic ring include a thiophenering, a furan ring, a benzothiophene ring, and a benzofuran ring.

Further, the aromatic heterocyclic ring which constitutes the aromaticheterocyclic group for Ra⁰¹ may be substituted with a substituent.Examples of substituents include an alkyl group, an alkoxy group, ahalogen atom, a halogenated alkyl group, and a hydroxyl group.

As the alkyl group for the substituent, an alkyl group of 1 to 5 carbonatoms is preferable, and a methyl group, an ethyl group, a propyl group,an n-butyl group or a tert-butyl group is more preferable.

The aforementioned alkoxy group as a substituent is preferably an alkoxygroup having 1 to 5 carbon atoms, more preferably a methoxy group, anethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxygroup or a tert-butoxy group, still more preferably a methoxy group oran ethoxy group, and most preferably a methoxy group.

Examples of the halogen atom as the substituent include a fluorine atom,a chlorine atom, a bromine atom and an iodine atom.

Example of the halogenated alkyl group as the substituent includes agroup in which part or all of the hydrogen atoms within theaforementioned alkyl group have been substituted with the aforementionedhalogen atoms.

Specific examples of the case where Ra⁰¹ represents an aromaticheterocyclic group containing an oxygen atom or a sulfur atom are shownbelow. In the formulae, “*” indicates a valence bond which is bonded tothe tertiary carbon atom (*C).

In formula (a0-1), examples of the alkyl group for Ra⁰¹ include a linearor branched alkyl group, and an alicyclic group.

The linear alkyl group for Ra⁰¹ preferably has 1 to 5 carbon atoms, morepreferably 1 to 4 carbon atoms, and still more preferably 1 or 2 carbonatoms. Specific examples include a methyl group, an ethyl group, ann-propyl group, an n-butyl group and an n-pentyl group. Among these, amethyl group, an ethyl group or an n-butyl group is preferable, and amethyl group or an ethyl group is more preferable.

The branched alkyl group for Ra⁰¹ preferably has 3 to 10 carbon atoms,and more preferably 3 to 5 carbon atoms. Specific examples include anisopropyl group, an isobutyl group, a tert-butyl group, an isopentylgroup, a neopentyl group a 1,1-diethylpropyl group and a2,2-dimethylbutyl group. Among these, an isopropyl group is preferable.

The alicyclic group for Ra⁰¹ may be a monocyclic group or a polycyclicgroup.

As the monocyclic alicyclic group, a group in which 1 hydrogen atom hasbeen removed from a monocycloalkane is preferable. The monocycloalkanepreferably has 3 to 6 carbon atoms, and specific examples thereofinclude cyclopentane and cyclohexane.

As the polycyclic alicyclic group, a group in which 1 hydrogen atom hasbeen removed from a polycycloalkane is preferable, and the polycyclicgroup preferably has 7 to 12 carbon atoms. Examples of thepolycycloalkane include adamantane, norbornane, isobornane,tricyclodecane and tetracyclododecane.

In formula (a0-1), in the case where Ra⁰¹ is an aromatic heterocyclicgroup containing an oxygen atom or a sulfur atom, Ra⁰² is a group whichforms an aliphatic cyclic group together with the tertiary carbon atom(*C) to which Ra⁰¹ is bonded, provided that the aliphatic cyclic groupcontains an electron-withdrawing group as a substituent.

The aliphatic cyclic group formed by Ra⁰² and the tertiary carbon atom(*C) to which Ra⁰¹ is bonded preferably has 3 to 20 carbon atoms, morepreferably 3 to 12 carbon atoms, still more preferably 4 to 8 carbonatoms, and most preferably 4 to 6 carbon atoms. Here, the number ofcarbon atoms include the tertiary carbon atom (*C). Further, thealiphatic cyclic group contains an electron-withdrawing group as asubstituent.

The aliphatic cyclic group formed by Ra⁰² and the tertiary carbon atom(*C) may be a polycyclic group or a monocyclic group, and is preferablya monocyclic group.

As the monocyclic aliphatic hydrocarbon group (in a state where theelectron-withdrawing group as a substituent is not included), a group inwhich two hydrogen atoms have been removed from a monocycloalkane ispreferable. The monocycloalkane preferably has 5 to 7 carbon atoms, andspecific examples thereof include cyclopentane, cyclohexane andcycloheptane. As the polycyclic aliphatic hydrocarbon group (in a statewhere the electron-withdrawing group as a substituent is not included),a group in which two hydrogen atoms have been removed from apolycycloalkane is preferable. The polycycloalkane preferably has 7 to12 carbon atoms, and specific examples thereof include adamantane,norbornane, isobornane, tricyclodecane and tetracyclododecane.

Specific examples of the aliphatic cyclic group formed by Ra⁰² and thetertiary carbon atom (*C) include a group in which part of the carbonatoms constituting the ring structure of the aforementioned aliphaticcyclic group has been substituted with an electron-withdrawing group asa substituent.

Examples of the electron-withdrawing group as a substituent include —O—,—C(═O)—O—, >C(═O), —S—, —S(═O)₂—, and —S(═O)₂—O—. Among these examples,—O—, >C(═O), and —S(═O)₂— are preferable.

Specific examples of the aliphatic cyclic group formed by Ra⁰² and thetertiary carbon atom (*C) to which Ra⁰¹ is bonded are shown below. Inthe formulae, “*1” indicates a valence bond which is bonded toW—C(═O)O—. “*2” indicates a valence bond which is bonded to Ra⁰¹.

In formula (a0-1), in the case where Ra⁰¹ is an alkyl group, Ra⁰² is agroup in which an aliphatic cyclic group forms a condensed ring togetherwith an aromatic heterocyclic group containing an oxygen atom or asulfur atom, provided that the aliphatic cyclic group is formed togetherwith the tertiary carbon atom (*C) to which Ra⁰¹ is bonded, and thealiphatic cyclic group contains an electron-withdrawing group as asubstituent. Thus, the aliphatic cyclic group contains the tertiarycarbon atoms (*C) to which Ra⁰¹ is bonded, and an electron-withdrawinggroup as a substituent.

The aliphatic cyclic group (which contains an electron-withdrawing groupas a substituent) within the condensed ring formed by Ra⁰² is the sameas defined for the aliphatic cyclic group formed by Ra⁰² and thetertiary carbon atom (*C) in the case where Ra⁰¹ is an aromaticheterocyclic group containing an oxygen atom or a sulfur atom.

The aromatic heterocyclic group containing an oxygen atom or a sulfuratom within the condensed ring formed by Ra⁰² is the same as defined forthe aromatic heterocyclic group containing an oxygen atom or a sulfuratom for Ra⁰¹.

Specific examples of the condensed ring formed by Ra⁰² are shown below.“*1” indicates a valence bond which is bonded to W—C(═O)O—.

Specific examples of the structural unit (a0) derived from a compoundrepresented by the aforementioned general formula (a0-1) are shownbelow. In the formulae shown below, R^(α) represents a hydrogen atom, amethyl group or a trifluoromethyl group.

Among these, as the structural unit (a0), at least one member selectedfrom the group consisting of structural units represented by generalformulae (a0-1-1) to (a0-1-25) shown below is preferable, and at leastone member selected from the group consisting of structural unitsrepresented by general formulae (a0-1-1) to (a0-1-21) shown below ismore preferable.

Among these examples, as the structural unit (a0), at least one memberselected from the group consisting of structural units represented byformulae (a0-1-1) to (a0-1-12) and (a0-1-15) to (a0-1-19) is mostpreferable.

As the structural unit (a0) contained in the component (A1), 1 kind ofstructural unit may be used, or 2 or more kinds of structural units maybe used.

In the component (A1), the amount of the structural unit (a0) based onthe combined total (100 mol %) of all structural units constituting thecomponent (A1) is preferably 20 to 80 mol %, more preferably 30 to 75mol %, and still more preferably 40 to 70 mol %.

When the amount of the structural unit (a0) is at least as large as thelower limit of the above preferable range, a resist pattern may bereliably obtained, and various lithography properties such as resolutionand roughness are further improved. On the other hand, when the amountis no more than the upper limit of the above preferable range, a goodbalance may be achieved with the other structural units.

Other Structural Units:

If desired, the component (A1) may include, in addition to thestructural unit (a0), other structural unit.

Examples of other structural units include a structural unit (a1)containing an acid decomposable group that exhibits increased polarityby the action of acid, (provided that the structural unit (a0) isexcluded); a structural unit (a2) containing a lactone-containing cyclicgroup, an —SO₂— containing cyclic group or a carbonate-containing cyclicgroup; a structural unit (a3) containing a polar group-containingaliphatic hydrocarbon group (provided that the structural units (a0),(a1) and (a2) are excluded); a structural unit (a4) containing an acidnon-dissociable aliphatic cyclic group; a structural unit (a10)represented by general formula (a10-1); and a structural unit derivedfrom styrene or a derivative thereof.

Structural Unit (a1):

In addition to the structural unit (a0), the component (A1) may includea structural unit (a1) containing an acid decomposable group thatexhibits increased polarity by the action of acid (provided thatstructural units which fall under the definition of the structural unit(a0) is excluded).

The term “acid decomposable group” refers to a group in which at least apart of the bond within the structure thereof is cleaved by the actionof an acid.

Examples of acid decomposable groups which exhibit increased polarity bythe action of an acid include groups which are decomposed by the actionof an acid to form a polar group.

Examples of the polar group include a carboxy group, a hydroxy group, anamino group and a sulfo group (—SO₃H). Among these, a polar groupcontaining —OH in the structure thereof (hereafter, referred to as“OH-containing polar group”) is preferable, a carboxy group or a hydroxygroup is more preferable, and a carboxy group is particularly desirable.

More specifically, as an example of an acid decomposable group, a groupin which the aforementioned polar group has been protected with an aciddissociable group (such as a group in which the hydrogen atom of theOH-containing polar group has been protected with an acid dissociablegroup) can be given.

The “acid dissociable group” refers to both (i) a group in which thebond between the acid dissociable group and the adjacent atom is cleavedby the action of acid; and (ii) a group in which one of the bonds iscleaved by the action of acid, and then a decarboxylation reactionoccurs, thereby cleaving the bond between the acid dissociable group andthe adjacent atom.

It is necessary that the acid dissociable group that constitutes theacid decomposable group is a group which exhibits a lower polarity thanthe polar group generated by the dissociation of the acid dissociablegroup. Thus, when the acid dissociable group is dissociated by theaction of acid, a polar group exhibiting a higher polarity than that ofthe acid dissociable group is generated, thereby increasing thepolarity. As a result, the polarity of the entire component (A1) isincreased. By the increase in the polarity, the solubility in an alkalideveloping solution changes, and the solubility in an alkali developingsolution is relatively increased, whereas the solubility in an organicdeveloping solution is relatively decreased.

Examples of the acid dissociable group for the structural unit (a1)include acid dissociable groups which have been proposed for a baseresin of a chemically amplified resist composition, provided that groupsdescribed above as the tertiary carbon atom-containing group within theaforementioned general formula (a0-1) are excluded.

Specific examples of acid dissociable groups for the base resin of aconventional chemically amplified resist include “acetal-type aciddissociable group”, “tertiary alkyl ester-type acid dissociable group”and “tertiary alkyloxycarbonyl acid dissociable group” described below.

Acetal-Type Acid Dissociable Group

Examples of the acid dissociable group for protecting the carboxy groupor hydroxy group as a polar group include the acid dissociable grouprepresented by general formula (a1-r-1) shown below (hereafter, referredto as “acetal-type acid dissociable group”).

In the formula, Ra′¹ and Ra′² represents a hydrogen atom or an alkylgroup; and Ra′³ represents a hydrocarbon group, provided that Ra′³ maybe bonded to Ra′¹ or Ra′².

In the formula (a1-r-1), it is preferable that at least one of Ra′¹ andRa′² represents a hydrogen atom, and it is more preferable that both ofRa′¹ and Ra′² represent a hydrogen atom.

In the case where Ra′¹ or Ra′² is an alkyl group, as the alkyl group,the same alkyl groups as those described above the for the substituentwhich may be bonded to the carbon atom on the α-position of theaforementioned α-substituted acrylate ester can be mentioned, and analkyl group of 1 to 5 carbon atoms is preferable. Specific examplesinclude linear or branched alkyl groups. Specific examples of the alkylgroup include a methyl group, an ethyl group, a propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group and a neopentyl group. Ofthese, a methyl group or an ethyl group is preferable, and a methylgroup is particularly preferable.

In formula (a1-r-1), examples of the hydrocarbon group for Ra′³ includea linear or branched alkyl group and a cyclic hydrocarbon group.

The linear alkyl group preferably has 1 to 5 carbon atoms, morepreferably 1 to 4, and still more preferably 1 or 2. Specific examplesinclude a methyl group, an ethyl group, an n-propyl group, an n-butylgroup and an n-pentyl group. Among these, a methyl group, an ethyl groupor an n-butyl group is preferable, and a methyl group or an ethyl groupis more preferable.

The branched alkyl group preferably has 3 to 10 carbon atoms, and morepreferably 3 to 5 carbon atoms. Specific examples include an isopropylgroup, an isobutyl group, a tert-butyl group, an isopentyl group, aneopentyl group a 1,1-diethylpropyl group and a 2,2-dimethylbutyl group.Among these, an isopropyl group is preferable.

In the case where Ra′³ represents a cyclic hydrocarbon group, the cyclichydrocarbon group may be an aliphatic hydrocarbon group or an aromatichydrocarbon group, and may be polycyclic or monocyclic.

As the monocyclic aliphatic hydrocarbon group, a group in which 1hydrogen atom has been removed from a monocycloalkane is preferable. Themonocycloalkane preferably has 3 to 6 carbon atoms, and specificexamples thereof include cyclopentane and cyclohexane.

As the polycyclic aliphatic hydrocarbon group, a group in which 1hydrogen atom has been removed from a polycycloalkane is preferable, andthe polycyclic group preferably has 7 to 12 carbon atoms. Examples ofthe polycycloalkane include adamantane, norbornane, isobornane,tricyclodecane and tetracyclododecane.

When the monovalent hydrocarbon group for Ra′³ is an aromatichydrocarbon group, the aromatic hydrocarbon group is a hydrocarbon grouphaving at least one aromatic ring.

The aromatic ring is not particularly limited, as long as it is a cyclicconjugated compound having (4n+2)π electrons, and may be eithermonocyclic or polycyclic. The aromatic ring preferably has 5 to 30carbon atoms, more preferably 5 to 20 carbon atoms, and still morepreferably 6 to 15 carbon atoms, and most preferably 6 to 12 carbonatoms. Examples of the aromatic ring include aromatic hydrocarbon rings,such as benzene, naphthalene, anthracene and phenanthrene; and aromatichetero rings in which part of the carbon atoms constituting theaforementioned aromatic hydrocarbon rings has been substituted with ahetero atom. Examples of the hetero atom within the aromatic heterorings include an oxygen atom, a sulfur atom and a nitrogen atom.Specific examples of the aromatic hetero ring include a pyridine ringand a thiophene ring.

Specific examples of the aromatic hydrocarbon group for Ra′³ include agroup in which one hydrogen atom has been removed from theaforementioned aromatic hydrocarbon ring or aromatic hetero ring (arylgroup or heteroaryl group); a group in which one hydrogen atom has beenremoved from an aromatic compound having two or more aromatic rings(biphenyl, fluorene or the like); and a group in which one hydrogen atomof the aforementioned aromatic hydrocarbon ring or aromatic hetero ringhas been substituted with an alkylene group (an arylalkyl group such asa benzyl group, a phenethyl group, a 1-naphthylmethyl group, a2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethylgroup). The alkylene group bonded to the aforementioned aromatichydrocarbon ring or the aromatic hetero ring preferably has 1 to 4carbon atoms, more preferably 1 or 2 carbon atoms, and most preferably 1carbon atom.

In the case where Ra′³ is bonded to Ra′¹ or Ra′² to form a ring, thecyclic group is preferably a 4 to 7-membered ring, and more preferably a4 to 6-membered ring. Specific examples of the cyclic group includetetrahydropyranyl group and tetrahydrofuranyl group.

Tertiary Alkyl Ester-Type Acid Dissociable Group

Examples of the acid dissociable group for protecting the carboxy groupas a polar group include the acid dissociable group represented bygeneral formula (a1-r-2) shown below. Among the acid dissociable groupsrepresented by general formula (a1-r-2), for convenience, a group whichis constituted of alkyl groups is referred to as “tertiary ester-typeacid dissociable group”.

In the formula, Ra′⁴ to Ra′⁶ each independently represents a hydrocarbongroup, provided that Ra′⁵ and Ra′⁶ may be mutually bonded to form aring.

As the hydrocarbon group for Ra′⁴ to Ra′⁶, the same groups as thosedescribed above for Ra′³, and a chain alkenyl group may be mentioned.The chain alkenyl group may be linear or branched, and preferably has 2to 10 carbon atoms, more preferably 2 to 5 carbon atoms, still morepreferably 2 to 4 carbon atoms, and most preferably 3 carbon atoms.Examples of linear alkenyl groups include a vinyl group, a propenylgroup (an allyl group) and a butynyl group. Examples of branched alkenylgroups include a 1-methylvinyl group, a 2-methylvinyl group, a1-methylpropenyl group and a 2-methylpropenyl group. Among theseexamples, as the chain-like alkenyl group, a linear alkenyl group ispreferable, a vinyl group or a propenyl group is more preferable, and avinyl group is most preferable.

Ra′⁴ is preferably a group in which one hydrogen atom has been removedfrom an aromatic hydrocarbon ring or an aromatic heterocyclic ring (anaryl group or a heteroaryl group), or an alkyl group having 1 to 5carbon atoms. In the case where Ra′⁵ and Ra′⁶ are mutually bonded toform a ring, a group represented by general formula (a1-r2-1) shownbelow can be mentioned. On the other hand, in the case where Ra′⁴ toRa′⁶ are not mutually bonded and independently represent a hydrocarbongroup, the group represented by general formula (a1-r2-2) shown belowcan be mentioned.

In the formulae, Ra′¹⁰ represents a hydrocarbon group of 1 to 10 carbonatoms; Ra′¹¹ is a group which forms an aliphatic cyclic group togetherwith a carbon atom having Ra′¹⁰ bonded thereto; and Ra′¹² to Ra′¹⁴ eachindependently represents a hydrocarbon group.

In the formula (a1-r2-1), as the hydrocarbon group of 1 to 10 carbonatoms for Ra′¹⁰, the same groups as described above for the linear orbranched alkyl group for Ra′³ in the formula (a1-r-1) are preferable.

In formula (a1-r2-1), the aliphatic cyclic group which is formed byRa′¹¹ together with the carbon atom bonded to Ra′¹⁰, the same groups asthose described above for the monocyclic or polycyclic aliphatichydrocarbon group for Ra′³ in formula (a1-r-1) are preferable. Further,part of the carbon atoms constituting the monocyclic group or thepolycyclic group as the aliphatic hydrocarbon group may be substitutedwith a hetero atom to form a heterocyclic group. Examples of the heteroatom within the heterocyclic group include an oxygen atom, a sulfur atomand a nitrogen atom.

In the formula (a1-r2-2), it is preferable that Ra′¹² and Ra′¹⁴ eachindependently represents an alkyl group or 1 to 10 carbon atoms, and itis more preferable that the alkyl group is the same group as thedescribed above for the linear or branched alkyl group for Ra′³ in theformula (a1-r-1), it is still more preferable that the alkyl group is alinear alkyl group of 1 to 5 carbon atoms, and it is particularlypreferable that the alkyl group is a methyl group or an ethyl group.

In the formula (a1-r2-2), it is preferable that Ra′¹³ is the same groupas described above for the linear or branched alkyl group or monocyclicor polycyclic alicyclic hydrocarbon group for Ra′³ in the formula(a1-r-1). Among these examples, monocyclic or polycyclic aliphatichydrocarbon group for Ra′³ are more preferable. Further, part of thecarbon atoms constituting the monocyclic group or the polycyclic groupas the aliphatic hydrocarbon group may be substituted with a hetero atomto form a heterocyclic group. Examples of the hetero atom within theheterocyclic group include an oxygen atom, a sulfur atom and a nitrogenatom.

Specific examples of the group represented by the aforementioned formula(a1-r2-1) are shown below. and * represents a valence bond.

Specific examples of the group represented by the aforementioned formula(a1-r2-2) are shown below.

Tertiary Alkyloxycarbonyl Acid Dissociable Group

Examples of the acid dissociable group for protecting a hydroxy group asa polar group include the acid dissociable group represented by generalformula (a1-r-3) shown below (hereafter, for convenience, referred to as“tertiary alkyloxycarbonyl-type acid dissociable group”).

In the formula, Ra′⁷ to Ra′⁹ each independently represents an alkylgroup.

In formula (a1-r-3), each of Ra′⁷ to Ra′⁹ is preferably an alkyl grouphaving 1 to 5 carbon atoms, and more preferably an alkyl group having 1to 3 carbon atoms.

Further, the total number of carbon atoms in the alkyl groups ispreferably 3 to 7, more preferably 3 to 5, and still more preferably 3or 4.

Examples of the structural unit (a1) include a structural unit derivedfrom an acrylate ester which may have the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent; astructural unit derived from an acrylamide; a structural unit derivedfrom hydroxystyrene or a hydroxystyrene derivative in which at least apart of the hydrogen atom of the hydroxy group is protected with asubstituent containing an acid decomposable group; and a structural unitderived from vinylbenzoic acid or a vinylbenzoic acid derivative inwhich at least a part of the hydrogen atom within —C(═O)—OH is protectedwith a substituent containing an acid decomposable group.

As the structural unit (a1), a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent is preferable.

Specific examples of preferable structural units for the structural unit(a1) include structural units represented by general formula (a1-1) or(a1-2) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Va¹represents a divalent hydrocarbon group which may contain an ether bond;n_(a1) each independently represents an integer of 0 to 2; and Ra¹represents an acid dissociable group represented by the aforementionedformula (a1-r-1) or (a1-r-2). Wa¹ represents a hydrocarbon group havinga valency of n_(a2)+1; n_(a2) represents an integer of 1 to 3; and Ra²represents an acid dissociable group represented by the aforementionedformula (a1-r-1) or (a1-r-3).

In the aforementioned formula (a1-1), as the alkyl group of 1 to 5carbon atoms for R, a linear or branched alkyl group of 1 to 5 carbonatoms is preferable, and specific examples thereof include a methylgroup, an ethyl group, a propyl group, an isopropyl group, an n-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group and a neopentyl group. The halogenated alkyl group of 1to 5 carbon atoms represented by R is a group in which part or all ofthe hydrogen atoms of the aforementioned alkyl group of 1 to 5 carbonatoms have been substituted with halogen atoms. Examples of the halogenatom include a fluorine atom, a chlorine atom, a bromine atom and aniodine atom, and a fluorine atom is particularly desirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and ahydrogen atom or a methyl group is particularly desirable in terms ofindustrial availability.

In formula (a1-1), Va¹ represents a divalent hydrocarbon group which mayhave an ether bond. The divalent hydrocarbon group for Va¹ may be analiphatic hydrocarbon group or an aromatic hydrocarbon group.

The aliphatic hydrocarbon group as the divalent hydrocarbon group forVa¹ may be either saturated or unsaturated. In general, the aliphatichydrocarbon group is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear orbranched aliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

The linear aliphatic hydrocarbon group preferably has 1 to 10 carbonatoms, more preferably 1 to 6, still more preferably 1 to 4, and mostpreferably 1 to 3.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—] and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group preferably has 2 to 10 carbonatoms, more preferably 3 to 6 carbon atoms, still more preferably 3 or 4carbon atoms, and most preferably 3 carbon atoms.

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

As examples of the hydrocarbon group containing a ring in the structurethereof, an alicyclic hydrocarbon group (a group in which two hydrogenatoms have been removed from an aliphatic hydrocarbon ring), a group inwhich the alicyclic hydrocarbon group is bonded to the terminal of theaforementioned chain-like aliphatic hydrocarbon group, and a group inwhich the alicyclic group is interposed within the aforementioned linearor branched aliphatic hydrocarbon group, can be given. The linear orbranched aliphatic hydrocarbon group is the same as defined for theaforementioned linear aliphatic hydrocarbon group or the aforementionedbranched aliphatic hydrocarbon group.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either a monocyclic group or apolycyclic group. As the monocyclic aliphatic hydrocarbon group, a groupin which 2 hydrogen atoms have been removed from a monocycloalkane ispreferable. The monocycloalkane preferably has 3 to 6 carbon atoms, andspecific examples thereof include cyclopentane and cyclohexane. As thepolycyclic group, a group in which two hydrogen atoms have been removedfrom a polycycloalkane is preferable, and the polycyclic grouppreferably has 7 to 12 carbon atoms. Examples of the polycycloalkaneinclude adamantane, norbornane, isobornane, tricyclodecane andtetracyclododecane.

The aromatic hydrocarbon group as the divalent hydrocarbon group for Va¹is a hydrocarbon group having an aromatic ring.

The aromatic hydrocarbon group preferably has 3 to 30 carbon atoms, morepreferably 5 to 30, still more preferably 5 to 20, still more preferably6 to 15, and most preferably 6 to 10. Here, the number of carbon atomswithin a substituent(s) is not included in the number of carbon atoms ofthe aromatic hydrocarbon group.

Examples of the aromatic ring contained in the aromatic hydrocarbongroup include aromatic hydrocarbon rings, such as benzene, biphenyl,fluorene, naphthalene, anthracene and phenanthrene; and aromatic heterorings in which part of the carbon atoms constituting the aforementionedaromatic hydrocarbon rings has been substituted with a hetero atom.Examples of the hetero atom within the aromatic hetero rings include anoxygen atom, a sulfur atom and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the aforementionedaromatic hydrocarbon ring (arylene group); and a group in which onehydrogen atom has been removed from the aforementioned aromatichydrocarbon ring (aryl group) and one hydrogen atom has been substitutedwith an alkylene group (such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group). The alkylene group (alkyl chainwithin the arylalkyl group) preferably has 1 to 4 carbon atom, morepreferably 1 or 2, and most preferably 1.

In the aforementioned formula (a1-2), the hydrocarbon group for Wa¹having a valency of n_(a2)+1 may be either an aliphatic hydrocarbongroup or an aromatic hydrocarbon group. The aliphatic cyclic grouprefers to a hydrocarbon group that has no aromaticity, and may be eithersaturated or unsaturated, but is preferably saturated. Examples of thealiphatic hydrocarbon group include a linear or branched aliphatichydrocarbon group, an aliphatic hydrocarbon group containing a ring inthe structure thereof, and a combination of the linear or branchedaliphatic hydrocarbon group and the aliphatic hydrocarbon groupcontaining a ring in the structure thereof.

The valency of n_(a2)+1 is preferably divalent, trivalent ortetravalent, and divalent or trivalent is more preferable.

Specific examples of structural unit represented by formula (a1-1) areshown below.

In the formulae shown below, R^(α) represents a hydrogen atom, a methylgroup or a trifluoromethyl group.

Specific examples of structural unit represented by formula (a1-2) areshown below.

As the structural unit (a1) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

When the component (A1) includes the structural unit (a1), the amount ofthe structural unit (a1) based on the combined total of all structuralunits constituting the component (A1) (100 mol %) is preferably 1 to 50mol %, more preferably 5 to 45 mol %, and still more preferably 5 to 30mol %.

When the amount of the structural unit (a1) is at least as large as thelower limit of the above-mentioned range, a resist pattern can bereliably obtained, and various lithography properties such assensitivity, resolution and roughness are further reduced. On the otherhand, when the amount of the structural unit (a1) is no more than theupper limit of the above-mentioned range, a good balance can be achievedwith the other structural units.

Structural Unit (a2):

The component (A1) may include, in addition to the structural unit (a0),a structural unit (a2) containing a lactone-containing cyclic group, an—SO₂— containing cyclic group or a carbonate-containing cyclic group.

When the component (A1) is used for forming a resist film, thelactone-containing cyclic group, the —SO₂— containing cyclic group orthe carbonate-containing cyclic group within the structural unit (a2) iseffective in improving the adhesion between the resist film and thesubstrate. Further, by virtue of including the structural unit (a2), inan alkali developing process, during developing, the solubility of theresist film in an alkali developing is enhanced.

The term “lactone-containing cyclic group” refers to a cyclic groupincluding a ring containing a —O—C(═O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings. The lactone-containing cyclic groupmay be either a monocyclic group or a polycyclic group.

The lactone-containing cyclic group for the structural unit (a2) is notparticularly limited, and an arbitrary structural unit may be used.Specific examples include groups represented by general formulae(a2-r-1) to (a2-r-7) shown below.

In the formulae, each Ra′²¹ independently represents a hydrogen atom, analkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group,a hydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyanogroup; R″ represents a hydrogen atom, an alkyl group, alactone-containing cyclic group, a carbonate-containing cyclic group oran —SO₂— containing cyclic group; A″ represents an oxygen atom, a sulfuratom, or an alkylene group of 1 to 5 carbon atoms which may contain anoxygen atom or a sulfur atom; n′ represents an integer of 0 to 2; and m′represents 0 or 1.

In formulae (a2-r-1) to (a2-r-7), the alkyl group for Ra′²¹ ispreferably an alkyl group of 1 to 6 carbon atoms. The alkyl group ispreferably a linear alkyl group or a branched alkyl group. Specificexamples include a methyl group, an ethyl group, a propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group, a neopentyl group and a hexylgroup. Among these, a methyl group or ethyl group is preferable, and amethyl group is most preferable.

The alkoxy group for Ra′²¹ is preferably an alkoxy group of 1 to 6carbon atoms.

The alkoxy group is preferably a linear or branched alkoxy group.Specific examples of the alkoxy groups include the aforementioned alkylgroups for Ra′²¹ having an oxygen atom (—O—) bonded thereto.

As examples of the halogen atom for Ra′²¹, a fluorine atom, chlorineatom, bromine atom and iodine atom can be given. Among these, a fluorineatom is preferable.

Examples of the halogenated alkyl group for Ra′²¹ include groups inwhich part or all of the hydrogen atoms within the aforementioned alkylgroup for Ra′²¹ has been substituted with the aforementioned halogenatoms. As the halogenated alkyl group, a fluorinated alkyl group ispreferable, and a perfluoroalkyl group is particularly desirable.

With respect to —COOR″ and —OC(═O)R″ for Ra′²¹, R″ represents a hydrogenatom, an alkyl group, a lactone-containing cyclic group, acarbonate-containing cyclic group or an —SO₂— containing cyclic group.

The alkyl group for R″ may be linear, branched or cyclic, and preferablyhas 1 to 15 carbon atoms.

When R″ represents a linear or branched alkyl group, it is preferably analkyl group of 1 to 10 carbon atoms, more preferably an alkyl group of 1to 5 carbon atoms, and most preferably a methyl group or an ethyl group.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and still morepreferably 5 to 10 carbon atoms. Specific examples include groups inwhich one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane which may or may not be substitutedwith a fluorine atom or a fluorinated alkyl group. Specific examplesinclude groups in which one or more hydrogen atoms have been removedfrom a monocycloalkane such as cyclopentane or cyclohexane; and groupsin which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

Examples of the lactone-containing cyclic group for R″ include groupsrepresented by the aforementioned general formulae (a2-r-1) to (a2-r-7).

The carbonate-containing cyclic group for R″ is the same as defined forthe carbonate-containing cyclic group described later. Specific examplesof the carbonate-containing cyclic group include groups represented bygeneral formulae (ax3-r-1) to (ax3-r-3).

The —SO₂— containing cyclic group for R″ is the same as defined for the—SO₂— containing cyclic group described later. Specific examples of the—SO₂— containing cyclic group include groups represented by generalformulae (a5-r-1) to (a5-r-4).

The hydroxyalkyl group for Ra′²¹ preferably has 1 to 6 carbon atoms, andspecific examples thereof include the alkyl groups for Ra′²¹ in which atleast one hydrogen atom has been substituted with a hydroxy group.

In formulae (a2-r-2), (a2-r-3) and (a2-r-5), as the alkylene group of 1to 5 carbon atoms represented by A″, a linear or branched alkylene groupis preferable, and examples thereof include a methylene group, anethylene group, an n-propylene group and an isopropylene group. Examplesof alkylene groups that contain an oxygen atom or a sulfur atom includethe aforementioned alkylene groups in which —O— or —S— is bonded to theterminal of the alkylene group or present between the carbon atoms ofthe alkylene group. Specific examples of such alkylene groups include—O—CH₂—, —CH₂—O—CH₂—, —S—CH₂—, and —CH₂—S—CH₂—. As A″, an alkylene groupof 1 to 5 carbon atoms or —O— is preferable, more preferably an alkylenegroup of 1 to 5 carbon atoms, and most preferably a methylene group.

Specific examples of the groups represented by the aforementionedgeneral formulae (a2-r-1) to (a2-r-7) are shown below.

An “—SO₂— containing cyclic group” refers to a cyclic group having aring containing —SO₂— within the ring structure thereof, i.e., a cyclicgroup in which the sulfur atom (S) within —SO₂— forms part of the ringskeleton of the cyclic group. The ring containing —SO₂— within the ringskeleton thereof is counted as the first ring. A cyclic group in whichthe only ring structure is the ring that contains —SO₂— in the ringskeleton thereof is referred to as a monocyclic group, and a groupcontaining other ring structures is described as a polycyclic groupregardless of the structure of the other rings. The —SO₂— containingcyclic group may be either a monocyclic group or a polycyclic group.

As the —SO₂— containing cyclic group, a cyclic group containing —O—SO₂—within the ring skeleton thereof, i.e., a cyclic group containing asultone ring in which —O—S— within the —O—SO₂— group forms part of thering skeleton thereof is particularly desirable.

More specific examples of the —SO₂— containing cyclic group includegroups represented by general formulas (a5-r-1) to (a5-r-4) shown below.

In the formulae, each Ra′⁵¹ independently represents an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, —COOR″,—OC(═O)R″, a hydroxyalkyl group or a cyano group; R″ represents ahydrogen atom, an alkyl group, a lactone-containing cyclic group, acarbonate-containing cyclic group or an —SO₂— containing cyclic group;A″ represents an oxygen atom, a sulfur atom, or an alkylene group of 1to 5 carbon atoms with or without an oxygen atom or a sulfur atom;

and n′ represents an integer of 0 to 2.

In general formulae (a5-r-1) and (a5-r-2), A″ is the same as defined forA″ in general formulae (a2-r-2), (a2-r-3) and (a2-r-5).

Examples of the alkyl group, alkoxy group, halogen atom, halogenatedalkyl group, —COOR″, —OC(═O)R″ and hydroxyalkyl group for Ra′⁵¹ includethe same groups as those described above in the explanation of Ra′²¹ inthe general formulas (a2-r-1) to (a2-r-7).

Specific examples of the groups represented by the aforementionedgeneral formulae (a5-r-1) to (a5-r-4) are shown below. In the formulaeshown below, “Ac” represents an acetyl group.

The term “carbonate-containing cyclic group” refers to a cyclic groupincluding a ring containing a —O—C(═O)—O— structure (carbonate ring).The term “carbonate ring” refers to a single ring containing a—O—C(═O)—O— structure, and this ring is counted as the first ring. Acarbonate-containing cyclic group in which the only ring structure isthe carbonate ring is referred to as a monocyclic group, and groupscontaining other ring structures are described as polycyclic groupsregardless of the structure of the other rings. The carbonate-containingcyclic group may be either a monocyclic group or a polycyclic group.

The carbonate-containing cyclic group is not particularly limited, andan arbitrary group may be used. Specific examples include groupsrepresented by general formulae (ax3-r-1) to (ax3-r-3) shown below.

In the formulae, each Ra′^(x31) independently represents an alkyl group,an alkoxy group, a halogen atom, a halogenated alkyl group, —COOR″,—OC(═O)R″, a hydroxyalkyl group or a cyano group; R″ represents ahydrogen atom, an alkyl group, a lactone-containing cyclic group, acarbonate-containing cyclic group or an —SO₂— containing cyclic group;A″ represents an oxygen atom, a sulfur atom, or an alkylene group of 1to 5 carbon atoms with or without an oxygen atom or a sulfur atom; p′represents an integer of 0 to 3; and q′ is 0 or 1.

In general formulae (ax3-r-2) and (ax3-r-3), A″ is the same as definedfor A″ in general formulae (a2-r-2), (a2-r-3) and (a2-r-5).

Examples of the alkyl group, alkoxy group, halogen atom, halogenatedalkyl group, —COOR″, —OC(═O)R″ and hydroxyalkyl group for Ra′³¹ includethe same groups as those described above in the explanation of Ra′²¹ inthe general formulas (a2-r-1) to (a2-r-7).

Specific examples of the groups represented by the aforementionedgeneral formulae (ax3-r-1) to (ax3-r-3) are shown below.

As the structural unit (a2), a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent is preferable.

Specific examples of preferable structural units for the structural unit(a2) include structural units represented by general formula (a2-1)shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Ya²¹represents a single bond or a divalent linking group; La²¹ represents—O—, —COO—, —CON(R′)—, —OCO—, —CONHCO— or —CONHCS—; and R′ represents ahydrogen atom or a methyl group; provided that, when La²¹ represents—O—, Ya²¹ does not represent —CO—; and Ra²¹ represents alactone-containing cyclic group, an —SO₂— containing cyclic group or acarbonate-containing cyclic group.

In the formula (a2-1), R is the same as defined above.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and ahydrogen atom or a methyl group is particularly desirable in terms ofindustrial availability.

In the formula (a2-1), the divalent linking group for Ya²¹ is notparticularly limited, and preferable examples thereof include a divalenthydrocarbon group which may have a substituent and a divalent linkinggroup containing a hetero atom.

The divalent hydrocarbon group for Ya²¹ is the same as defined for thedivalent hydrocarbon group represented by Va¹ in the aforementionedformula (a1-1). Examples of the substituent for the divalent hydrocarbongroup represented by Ya²¹ include an alkyl group of 1 to 5 carbon atoms,an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxygroup, a carbonyl group.

In the case where Ya²¹ represents a divalent linking group containing ahetero atom, preferable examples of the linking group include —O—,—C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH—, —NH—C(═NH)— (may besubstituted with a substituent such as an alkyl group, an acyl group orthe like), —S—, —S(═O)₂—, —S(═O)₂—O—, and a group represented by generalformula: —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—,—[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²— [inthe formulae, Y²¹ and Y²² each independently represents a divalenthydrocarbon group which may have a substituent, O represents an oxygenatom, and m′ represents an integer of 0 to 3].

In the case where the divalent linking group containing a hetero atom is—C(═O)—NH—, —C(═O)—NH—C(═O)—, —NH— or —NH—C(═NH)—, H may be substitutedwith a substituent such as an alkyl group, an acyl group or the like.The substituent (an alkyl group, an acyl group or the like) preferablyhas 1 to 10 carbon atoms, more preferably 1 to 8, and most preferably 1to 5.

In general formulae —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—,—[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²—, Y²¹and Y²² each independently represents a divalent hydrocarbon group whichmay have a substituent. Examples of the divalent hydrocarbon groupinclude the same groups as those described above as the “divalenthydrocarbon group which may have a substituent” in the explanation ofthe aforementioned divalent linking group.

As Y²¹, a linear aliphatic hydrocarbon group is preferable, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, and a methylene group or anethylene group is particularly desirable.

As Y²², a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group or an alkylmethylene group ismore preferable. The alkyl group within the alkylmethylene group ispreferably a linear alkyl group of 1 to 5 carbon atoms, more preferablya linear alkyl group of 1 to 3 carbon atoms, and most preferably amethyl group.

In the group represented by the formula —[Y²¹—C(═O)—O]_(m)″—Y²²—, m″represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1. Namely, it is particularlydesirable that the group represented by the formula—[Y²¹—C(═O)—O]_(m)″—Y²²— is a group represented by the formula—Y²¹—C(═O)—O—Y²²—. Among these, a group represented by the formula—(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′ is aninteger of 1 to 10, preferably an integer of 1 to 8, more preferably aninteger of 1 to 5, still more preferably 1 or 2, and most preferably 1.b′ is an integer of 1 to 10, preferably an integer of 1 to 8, morepreferably an integer of 1 to 5, still more preferably 1 or 2, and mostpreferably 1.

Ya²¹ preferably represents an ester bond [—C(═O)—O—], an ether bond(—O—), a linear or branched alkylene group, a combination of these, or asingle bond.

In formula (a2-1), La²¹ represents —O—, —COO—, —CON(R′)—, —OCO—,—CONHCO— or —CONHCS—.

R′ represents a hydrogen atom or a methyl group.

However, when La²¹ represents —O—, Ya²¹ does not represent —CO—.

In the formula (a2-1), Ra²¹ represents a lactone-containing cyclicgroup, an —SO₂— containing cyclic group or a carbonate-containing cyclicgroup.

Preferable examples of the lactone-containing cyclic group, the —SO₂—containing cyclic group and the carbonate-containing cyclic group forRa²¹ include groups represented by general formulae (a2-r-1) to(a2-r-7), groups represented by general formulae (a5-r-1) to (a5-r-4)and groups represented by general formulae (ax3-r-1) to (ax3-r-3).

Among the above examples, as Ra²¹, a lactone-containing cyclic group oran —SO₂— containing cyclic group is preferable, and a group representedby the aforementioned general formula (a2-r-1), (a2-r-2), (a2-r-6) or(a5-r-1) is more preferable. Specifically, a group represented by any ofchemical formulae (r-1c-1-1) to (r-1c-1-7), (r-1c-2-1) to (r-1c-2-18),(r-1c-6-1), (r-s1-1-1) and (r-s1-1-18) is still more preferable.

As the structural unit (a2) contained in the component (A1), 1 kind ofstructural unit may be used, or 2 or more kinds may be used.

When the component (A1) contains the structural unit (a2), the amount ofthe structural unit (a2) based on the combined total (100 mol %) of allstructural units constituting the component (A1) is preferably 1 to 80mol %, more preferably 3 to 70 mol %, still more preferably 5 to 60 mol%, and most preferably 10 to 50 mol %.

When the amount of the structural unit (a2) is at least as large as thelower limit of the above preferable range, the effect of using thestructural unit (a2) may be satisfactorily achieved. On the other hand,when the amount of the structural unit (a2) is no more than the upperlimit of the above preferable range, a good balance can be achieved withthe other structural units, and various lithography properties andpattern shape may be improved.

Structural Unit (a3):

The component (A1) may include, in addition to the structural unit (a0),a structural unit (a3) containing a polar group-containing aliphatichydrocarbon group (provided that the structural units that fall underthe definition of structural units (a0), (a1) and (a2) are excluded).

When the component (A1) includes the structural unit (a3), thehydrophilicity of the component (A1) is enhanced, thereby contributingto improvement in resolution.

Examples of the polar group include a hydroxyl group, cyano group,carboxyl group, or hydroxyalkyl group in which part of the hydrogenatoms of the alkyl group have been substituted with fluorine atoms,although a hydroxyl group is particularly desirable.

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (preferably alkylene groups) of 1 to 10 carbon atoms,and cyclic aliphatic hydrocarbon groups (cyclic groups). These cyclicgroups can be selected appropriately from the multitude of groups thathave been proposed for the resins of resist compositions designed foruse with ArF excimer lasers. The cyclic group is preferably a polycyclicgroup, more preferably a polycyclic group of 7 to 30 carbon atoms.

Of the various possibilities, structural units derived from an acrylateester that include an aliphatic polycyclic group that contains ahydroxyl group, cyano group, carboxyl group or a hydroxyalkyl group inwhich part of the hydrogen atoms of the alkyl group have beensubstituted with fluorine atoms are particularly desirable. Examples ofthe polycyclic group include groups in which two or more hydrogen atomshave been removed from a bicycloalkane, tricycloalkane, tetracycloalkaneor the like. Specific examples include groups in which two or morehydrogen atoms have been removed from a polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane. Of these polycyclic groups, groups in which two ormore hydrogen atoms have been removed from adamantane, norbornane ortetracyclododecane are preferred industrially.

As the structural unit (a3), there is no particular limitation as longas it is a structural unit containing a polar group-containing aliphatichydrocarbon group, and an arbitrary structural unit may be used.

The structural unit (a3) is preferably a structural unit derived from anacrylate ester which may have the hydrogen atom bonded to the carbonatom on the α-position substituted with a substituent and contains apolar group-containing aliphatic hydrocarbon group.

When the aliphatic hydrocarbon group within the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon group of1 to 10 carbon atoms, the structural unit (a3) is preferably astructural unit derived from a hydroxyethyl ester of acrylic acid. Onthe other hand, when the hydrocarbon group is a polycyclic group,structural units represented by formulas (a3-1), (a3-2) and (a3-3) shownbelow are preferable.

In the formulas, R is the same as defined above; j is an integer of 1 to3; k is an integer of 1 to 3; t′ is an integer of 1 to 3; 1 is aninteger of 1 to 5; and s is an integer of 1 to 3.

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When jis 2, it is preferable that the hydroxyl groups be bonded to the 3rd and5th positions of the adamantyl group. When j is 1, it is preferable thatthe hydroxyl group be bonded to the 3rd position of the adamantyl group.

j is preferably 1, and it is particularly desirable that the hydroxylgroup be bonded to the 3rd position of the adamantyl group.

In formula (a3-2), k is preferably 1. The cyano group is preferablybonded to the 5th or 6th position of the norbornyl group.

In formula (a3-3), t′ is preferably 1. l is preferably 1. s ispreferably 1. Further, it is preferable that a 2-norbornyl group or3-norbornyl group be bonded to the terminal of the carboxy group of theacrylic acid. The fluorinated alkyl alcohol is preferably bonded to the5th or 6th position of the norbornyl group.

As the structural unit (a3) contained in the component (A1), 1 kind ofstructural unit may be used, or 2 or more kinds of structural units maybe used.

When the component (A1) contains the structural unit (a3), the amount ofthe structural unit (a3) based on the combined total (100 mol %) of allstructural units constituting the component (A1) is preferably 1 to 50mol %, more preferably 3 to 40 mol %, still more preferably 5 to 30 mol%, and most preferably 10 to 30 mol %.

When the amount of the structural unit (a3) is at least as large as thelower limit of the above-mentioned preferable range, the resolution isimproved in the formation of a resist pattern. On the other hand, whenthe amount of the structural unit (a3) is no more than the upper limitof the above-mentioned preferable range, a good balance can be reliablyachieved with the other structural units.

Structural Unit (a4):

The component (A1) may be further include, in addition to the structuralunit (a0), a structural unit (a4) containing an acid non-dissociable,aliphatic cyclic group.

When the component (A1) includes the structural unit (a4), dry etchingresistance of the resist pattern to be formed is improved. Further, thehydrophobicity of the component (A) is further improved. Increase in thehydrophobicity contributes to improvement in terms of resolution, shapeof the resist pattern and the like, particularly in a solvent developingprocess.

An “acid non-dissociable, aliphatic cyclic group” in the structural unit(a4) refers to a cyclic group which is not dissociated by the action ofthe acid (e.g., acid generated from a structural unit which generatesacid upon exposure or acid generated from the component (B)) uponexposure, and remains in the structural unit.

As the structural unit (a4), a structural unit which contains anon-acid-dissociable aliphatic cyclic group, and is also derived from anacrylate ester is preferable. As the cyclic group, any of the multitudeof conventional polycyclic groups used within the resin component ofresist compositions for ArF excimer lasers or KrF excimer lasers (andparticularly for ArF excimer lasers) can be used.

As the aliphatic polycyclic group, at least one polycyclic groupselected from amongst a tricyclodecyl group, adamantyl group,tetracyclododecyl group, isobornyl group, and norbornyl group isparticularly desirable in consideration of industrial availability andthe like. These polycyclic groups may be substituted with a linear orbranched alkyl group of 1 to 5 carbon atoms.

Specific examples of the structural unit (a4) include structural unitsrepresented by general formulae (a4-1) to (a4-7) shown below.

In the formulae, R^(α) is the same as defined above.

As the structural unit (a4) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

When the component (A1) contains the structural unit (a4), the amount ofthe structural unit (a4) based on the combined total (100 mol %) of allstructural units constituting the component (A1) is preferably 1 to 40mol %, and more preferably 5 to 20 mol %.

When the amount of the structural unit (a4) is at least as large as thelower limit of the above-mentioned preferable range, the effect of usingthe structural unit (a4) can be satisfactorily achieved. On the otherhand, when the amount of the structural unit (a4) is no more than theupper limit of the above-mentioned preferable range, a good balance canbe achieved with the other structural units.

Structural Unit (a10):

The structural unit (a10) is a structural unit represented by generalformula (a10-1) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms;Ya^(x1) represents a single bond or a divalent linking group; Wa^(x1)represents an aromatic hydrocarbon group having a valency of(n_(ax1)+1); and n_(ax1) represents an integer of 1 or more.

In general formula (a10-1), R represents a hydrogen atom, an alkyl groupof 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbonatoms.

As the alkyl group for R, a linear or branched alkyl group of 1 to 5carbon atoms is preferable, and specific examples thereof include amethyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group and a neopentyl group.

The halogenated alkyl group of 1 to 5 carbon atoms represented by R is agroup in which part or all of the hydrogen atoms of the aforementionedalkyl group of 1 to 5 carbon atoms have been substituted with halogenatoms. Examples of the halogen atom include a fluorine atom, a chlorineatom, a bromine atom and an iodine atom, and a fluorine atom isparticularly desirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and inview of industrial availability, a hydrogen atom, a methyl group or atrifluoromethyl group is more preferable, a hydrogen atom or a methylgroup is still more preferable, and a methyl group is most preferable.

In formula (a10-1), Ya^(x1) represents a single bond or a divalentlinking group.

In the aforementioned chemical formula, the divalent linking group forYa^(x1) is not particularly limited, and preferable examples thereofinclude a divalent hydrocarbon group which may have a substituent and adivalent linking group containing a hetero atom.

Divalent Hydrocarbon Group which May have a Substituent:

In the case where Ya^(x1) is a divalent linking group which may have asubstituent, the hydrocarbon group may be either an aliphatichydrocarbon group or an aromatic hydrocarbon group.

Aliphatic Hydrocarbon Group for Ya^(x1)

An “aliphatic hydrocarbon group” refers to a hydrocarbon group that hasno aromaticity. The aliphatic hydrocarbon group may be saturated orunsaturated. In general, the aliphatic hydrocarbon group is preferablysaturated.

Examples of the aliphatic hydrocarbon group include a linear or branchedaliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

Linear or Branched Aliphatic Hydrocarbon Group

The linear aliphatic hydrocarbon group preferably has 1 to 10 carbonatoms, more preferably 1 to 6, still more preferably 1 to 4, and mostpreferably 1 to 3.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—] and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group preferably has 2 to 10 carbonatoms, more preferably 3 to 6, still more preferably 3 or 4, and mostpreferably 3.

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include a fluorine atom, afluorinated alkyl group of 1 to 5 carbon atoms, and a carbonyl group.

Aliphatic Hydrocarbon Group Containing a Ring in the Structure Thereof

As examples of the hydrocarbon group containing a ring in the structurethereof, a cyclic aliphatic hydrocarbon group containing a hetero atomin the ring structure thereof and may have a substituent (a group inwhich two hydrogen atoms have been removed from an aliphatic hydrocarbonring), a group in which the cyclic aliphatic hydrocarbon group is bondedto the terminal of the aforementioned chain-like aliphatic hydrocarbongroup, and a group in which the cyclic aliphatic group is interposedwithin the aforementioned linear or branched aliphatic hydrocarbongroup, can be given. As the linear or branched aliphatic hydrocarbongroup, the same groups as those described above can be used.

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbonatoms, and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be either a polycyclic groupor a monocyclic group. As the monocyclic aliphatic hydrocarbon group, agroup in which 2 hydrogen atoms have been removed from a monocycloalkaneis preferable. The monocycloalkane preferably has 3 to 6 carbon atoms,and specific examples thereof include cyclopentane and cyclohexane. Asthe polycyclic group, a group in which 2 hydrogen atoms have beenremoved from a polycycloalkane is preferable, and the polycyclic grouppreferably has 7 to 12 carbon atoms. Examples of the polycycloalkaneinclude adamantane, norbornane, isobornane, tricyclodecane andtetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup and a carbonyl group.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and more preferably a methyl group, an ethyl group, apropyl group, an n-butyl group or a tert-butyl group.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and still more preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned alkyl groups has been substituted with the aforementionedhalogen atoms.

The cyclic aliphatic hydrocarbon group may have part of the carbon atomsconstituting the ring structure thereof substituted with a substituentcontaining a hetero atom. As the substituent containing a hetero atom,—O—, —C(═O)—O—, —S—, —S(═O)₂— or —S(═O)₂—O— is preferable.

Aromatic Hydrocarbon Group for Ya^(x1)

The aromatic hydrocarbon group is a hydrocarbon group having at leastone aromatic ring.

The aromatic ring is not particularly limited, as long as it is a cyclicconjugated compound having (4n+2)π electrons, and may be eithermonocyclic or polycyclic. The aromatic ring preferably has 5 to 30carbon atoms, more preferably 5 to 20 carbon atoms, and still morepreferably 6 to 15 carbon atoms, and most preferably 6 to 12 carbonatoms. Here, the number of carbon atoms within a substituent(s) is notincluded in the number of carbon atoms of the aromatic hydrocarbongroup.

Examples of the aromatic ring include aromatic hydrocarbon rings, suchas benzene, naphthalene, anthracene and phenanthrene; and aromatichetero rings in which part of the carbon atoms constituting theaforementioned aromatic hydrocarbon rings has been substituted with ahetero atom. Examples of the hetero atom within the aromatic heterorings include an oxygen atom, a sulfur atom and a nitrogen atom.Specific examples of the aromatic hetero ring include a pyridine ringand a thiophene ring.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the aforementionedaromatic hydrocarbon ring or aromatic hetero ring (arylene group orheteroarylene group); a group in which two hydrogen atoms have beenremoved from an aromatic compound having two or more aromatic rings(biphenyl, fluorene or the like); and a group in which one hydrogen atomof the aforementioned aromatic hydrocarbon ring or aromatic hetero ringhas been substituted with an alkylene group (a group in which onehydrogen atom has been removed from the aryl group within theaforementioned arylalkyl group such as a benzyl group, a phenethylgroup, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a1-naphthylethyl group, or a 2-naphthylethyl group, or a heteroarylalkylgroup). The alkylene group which is bonded to the aforementioned arylgroup or heteroaryl group preferably has 1 to 4 carbon atoms, morepreferably 1 or 2 carbon atoms, and most preferably 1 carbon atom.

With respect to the aromatic hydrocarbon group, the hydrogen atom withinthe aromatic hydrocarbon group may be substituted with a substituent.For example, the hydrogen atom bonded to the aromatic ring within thearomatic hydrocarbon group may be substituted with a substituent.Examples of substituents include an alkyl group, an alkoxy group, ahalogen atom, a halogenated alkyl group, and a hydroxyl group.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and more preferably a methyl group, an ethyl group, apropyl group, an n-butyl group or a tert-butyl group.

As the alkoxy group, the halogen atom and the halogenated alkyl groupfor the substituent, the same groups as the aforementioned substituentgroups for substituting a hydrogen atom within the cyclic aliphatichydrocarbon group can be used.

Divalent Linking Group Containing a Hetero Atom

In the case where Ya^(x1) represents a divalent linking group containinga hetero atom, preferable examples of the linking group include —O—,—C(═O)—O—, —O—C(═O)—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH—,—NH—C(═NH)— (may be substituted with a substituent such as an alkylgroup, an acyl group or the like), —S—, —S(═O)₂—, —S(═O)₂—O—, and agroup represented by general formula: —Y²¹—O—Y²²—, —Y²¹—O—,—Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—, —[Y²¹—C(═O)—O]_(m″)—Y²²—,—Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²— [in the formulae, Y²¹ and Y²²each independently represents a divalent hydrocarbon group which mayhave a substituent, O represents an oxygen atom, and m′ represents aninteger of 0 to 3].

In the case where the divalent linking group containing a hetero atom is—C(═O)—NH—, —C(═O)—NH—C(═O)—, —NH— or —NH—C(═NH)—, H may be substitutedwith a substituent such as an alkyl group, an acyl group or the like.The substituent (an alkyl group, an acyl group or the like) preferablyhas 1 to 10 carbon atoms, more preferably 1 to 8, and most preferably 1to 5.

In general formulae —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—,—[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²—, Y²¹and Y²² each independently represents a divalent hydrocarbon group whichmay have a substituent. Examples of the divalent hydrocarbon groupinclude the same groups as those described above as the “divalenthydrocarbon group which may have a substituent” in the explanation ofthe aforementioned divalent linking group for Ya^(x1).

As Y²¹, a linear aliphatic hydrocarbon group is preferable, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, and a methylene group or anethylene group is particularly desirable.

As Y²², a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group or an alkylmethylene group ismore preferable. The alkyl group within the alkylmethylene group ispreferably a linear alkyl group of 1 to 5 carbon atoms, more preferablya linear alkyl group of 1 to 3 carbon atoms, and most preferably amethyl group.

In the group represented by the formula —[Y²¹—C(═O)—O]_(m)″—Y²²—, m″represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1. Namely, it is particularlydesirable that the group represented by the formula—[Y²¹—C(═O)—O]_(m)″—Y²²— is a group represented by the formula—Y²¹—C(═O)—O—Y²²—. Among these, a group represented by the formula—(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′ is aninteger of 1 to 10, preferably an integer of 1 to 8, more preferably aninteger of 1 to 5, still more preferably 1 or 2, and most preferably 1.b′ is an integer of 1 to 10, preferably an integer of 1 to 8, morepreferably an integer of 1 to 5, still more preferably 1 or 2, and mostpreferably 1.

Among the above examples, as Ya^(x1), a single bond, an ester bond[—C(═O)—O—, —O—C(═O)—], an ether bond (—O—), a linear or branchedalkylene group, or a combination of these is preferable, and a singlebond or an ester bond [—C(═O)—O—, —O—C(═O)—] is more preferable.

In formula (a10-1), Wa^(x1) represents an aromatic hydrocarbon grouphaving a valency of (n_(ax1)+1).

Examples of the aromatic hydrocarbon group for Wa^(x1) include a groupobtained by removing (n_(ax1)+1) hydrogen atoms from an aromatic ring.The aromatic ring is not particularly limited, as long as it is a cyclicconjugated compound having (4n+2)π electrons, and may be eithermonocyclic or polycyclic. The aromatic ring preferably has 5 to 30carbon atoms, more preferably 5 to 20 carbon atoms, and still morepreferably 6 to 15 carbon atoms, and most preferably 6 to 12 carbonatoms. Specific examples of the aromatic ring include an aromatichydrocarbon ring, such as benzene, naphthalene, anthracene orphenanthrene; and an aromatic heterocyclic ring in which part of thecarbon atoms constituting the aromatic hydrocarbon ring has beensubstituted with a heteroatom. Examples of the hetero atom within thearomatic hetero rings include an oxygen atom, a sulfur atom and anitrogen atom. Specific examples of the aromatic hetero ring include apyridine ring and a thiophene ring.

Further examples of the aromatic hydrocarbon group for Wa^(x1) include agroup in which (n_(ax1)+1) hydrogen atom(s) has been removed from anaromatic group containing 2 or more aromatic rings (e.g., biphenyl,fluorene, or the like).

Among the above examples, as Wa^(x1), a group in which (n_(ax1)+1)hydrogen atoms have been removed from benzene, naphthalene, anthraceneor biphenyl is preferable, a group in which (n_(ax1)+1) hydrogen atomshave been removed from benzene or naphthalene is more preferable, and agroup in which (n_(ax1)+1) hydrogen atoms have been removed from benzeneis still more preferable.

In formula (a10-1), n_(ax1) is an integer of 1 or more, preferably aninteger of 1 to 10, more preferably an integer of 1 to 5, still morepreferably 1, 2 or 3, and most preferably 1 or 2.

Specific examples of the structural unit (a10) represented by formula(a10-1) are shown below.

In the formulae shown below, R^(α) represents a hydrogen atom, a methylgroup or a trifluoromethyl group.

As the structural unit (a10) contained in the component (A1), 1 kind ofstructural unit may be used, or 2 or more kinds of structural units maybe used.

When the component (A1) includes the structural unit (a10), the amountof the structural unit (a10) based on the combined total of allstructural units constituting the component (A1) (100 mol %) ispreferably 20 to 80 mol %, more preferably 20 to 70 mol %, still morepreferably 25 to 60 mol %, and most preferably 30 to 50 mol %.

When the amount of the structural unit (a10) is at least as large as thelower limit of the above preferable range, the sensitivity may be morereliably enhanced. On the other hand, when the amount of the structuralunit (a10) is no more than the upper limit of the above-mentioned range,a good balance may be reliably achieved with the other structural units.

Structural Unit Derived from Styrene or a Derivative Thereof (StructuralUnit (St))

The term “styrene” is a concept including styrene and compounds in whichthe hydrogen atom at the α-position of styrene is substituted with asubstituent such as an alkyl group or a halogenated alkyl group.Examples of the alkyl group as the substituent include an alkyl grouphaving 1 to 5 carbon atoms. Examples of the halogenated alkyl group asthe substituent include a halogenated alkyl group having 1 to 5 carbonatoms.

Examples of the “styrene derivative” include styrene which has asubstituent other than a hydroxy group bonded to the benzene ring andmay have the hydrogen atom on the α-position substituted with asubstituent.

Here, the α-position (carbon atom on the α-position) refers to thecarbon atom having the benzene ring bonded thereto, unless specifiedotherwise.

A “structural unit derived from styrene” or “structural unit derivedfrom a styrene derivative” refers to a structural unit that is formed bythe cleavage of the ethylenic double bond of styrene or a styrenederivative.

As the structural unit (st) contained in the component (A1), 1 kind ofstructural unit may be used, or 2 or more kinds of structural units maybe used.

When the component (A1) includes the structural unit (st), the amount ofthe structural unit (st) based on the combined total of all structuralunits constituting the component (A1) (100 mol %) is preferably 1 to 30mol %, and more preferably 3 to 20 mol %.

In the resist composition of the present embodiment, the resin component(A1) contains a polymer having the structural unit (a0) (hereafter, thispolymer is referred to as “component (A1-1)”). As the component (A1-1),1 kind of the polymer may be used, or 2 or more kinds of the polymersmay be used in combination.

The component (A1-1) preferably includes, for example, a copolymerhaving a structural unit (a0), a structural unit (a2) and any otherstructural unit if desired. Preferable examples of the component (A1-1)include a copolymer consisting of a repeating structure of a structuralunit (a0) and a structural unit (a2); and a copolymer consisting of arepeating structure of a structural unit (a0), a structural unit (a2)and a structural unit (a3).

Alternatively, the component (A1-1) preferably includes, for example, acopolymer having a structural unit (a0), a structural unit (a10) and anyother structural unit if desired. Preferable examples of such component(A1-1) include a copolymer consisting of a repeating structure of astructural unit (a0) and a structural unit (a10).

<<Component (A2)>>

In the resist composition of the present embodiment, as the component(A), “a base component which exhibits changed solubility in a developingsolution under action of acid” other than the component (A1) (hereafter,referred to as “component (A2)”) may be used in combination.

As the component (A2), there is no particular limitation, and any of themultitude of conventional base resins used within chemically amplifiedresist compositions may be arbitrarily selected for use.

As the component (A2), one kind of a polymer or a low molecular weightcompound may be used, or a combination of two or more kinds may be used.

In the component (A), the amount of the component (A1) based on thetotal weight of the component (A) is preferably 50% by weight or more,more preferably 75% by weight or more, still more preferably 90% byweight or more, and may be even 100% by weight.

When the amount of the component (A1) is at least as large as the lowerlimit of the above preferable range, sensitivity may be improved, and aresist pattern with improved lithography properties such as resolutionand reduced roughness may be reliably formed.

In the resist composition of the present embodiment, the amount of thecomponent (A) may be appropriately adjusted depending on the thicknessof the resist film to be formed, and the like.

<Other Components>

The resist composition of the present embodiment may contain, inaddition to the aforementioned component (A), any other components otherthan the component (A). Examples of the other components include thecomponent (B), the component (D), the component (E), the component (F)and the component (S) described below.

<<Acid-Generator Component (B)>>

The resist composition of the present embodiment may include, inaddition to the components (A), an acid-generator component (hereafter,sometimes referred to as “component (B)”).

As the component (B), there is no particular limitation, and any of theknown acid generators used in conventional chemically amplified resistcompositions can be used.

Examples of these acid generators are numerous, and include onium saltacid generators such as iodonium salts and sulfonium salts; oximesulfonate acid generators; diazomethane acid generators such as bisalkylor bisaryl sulfonyl diazomethanes and poly(bis-sulfonyl)diazomethanes;nitrobenzylsulfonate acid generators; iminosulfonate acid generators;and disulfone acid generators. Among these, it is preferable to use anonium salt acid generator.

As the onium salt acid generator, a compound represented by generalformula (b-1) below (hereafter, sometimes referred to as “component(b-1)”), a compound represented by general formula (b-2) below(hereafter, sometimes referred to as “component (b-2)”) or a compoundrepresented by general formula (b-3) below (hereafter, sometimesreferred to as “component (b-3)”) may be used.

In the formulae, R¹⁰¹ and R¹⁰⁴ to R¹⁰⁸ each independently represents acyclic group which may have a substituent, a chain-like alkyl groupwhich may have a substituent or a chain-like alkenyl group which mayhave a substituent, provided that R¹⁰⁴ and R¹⁰⁵ may be mutually bondedto form a ring;

R¹⁰² represents a fluorine atom or a fluorinated alkyl group of 1 to 5carbon atoms; Y¹⁰¹ represents a single bond or a divalent linking groupcontaining an oxygen atom; V¹⁰¹ to V¹⁰³ each independently represents asingle bond, an alkylene group or a fluorinated alkylene group; L¹⁰¹ andL¹⁰² each independently represents a single bond or an oxygen atom; L¹⁰³to L¹⁰⁵ each independently represents a single bond, —CO— or —SO₂—; mrepresents an integer of 1 or more; and M′^(m+) represents an m-valentonium cation.

{Anion Moiety}

Anion Moiety of Component (b-1)

In the formula (b-1), R¹⁰¹ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent.

Cyclic Group which May have a Substituent:

The cyclic group is preferably a cyclic hydrocarbon group, and thecyclic hydrocarbon group may be either an aromatic hydrocarbon group oran aliphatic hydrocarbon group. An “aliphatic hydrocarbon group” refersto a hydrocarbon group that has no aromaticity. The aliphatichydrocarbon group may be either saturated or unsaturated, but ingeneral, the aliphatic hydrocarbon group is preferably saturated.

The aromatic hydrocarbon group for R¹⁰¹ is a hydrocarbon group having anaromatic ring. The aromatic hydrocarbon group preferably has 3 to 30carbon atoms, more preferably 5 to 30 carbon atoms, still morepreferably 5 to 20 carbon atoms, still more preferably 6 to 15 carbonatoms, and most preferably 6 to 10 carbon atoms. Here, the number ofcarbon atoms within a substituent(s) is not included in the number ofcarbon atoms of the aromatic hydrocarbon group.

Examples of the aromatic ring contained in the aromatic hydrocarbongroup represented by R¹⁰¹ include benzene, fluorene, naphthalene,anthracene, phenanthrene and biphenyl; and aromatic hetero rings inwhich part of the carbon atoms constituting the aforementioned aromaticrings has been substituted with a hetero atom. Examples of the heteroatom within the aromatic hetero rings include an oxygen atom, a sulfuratom and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group represented by R¹⁰¹include a group in which one hydrogen atom has been removed from theaforementioned aromatic ring (i.e., an aryl group, such as a phenylgroup or a naphthyl group), and a group in which one hydrogen of theaforementioned aromatic ring has been substituted with an alkylene group(e.g., an arylalkyl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup or a 2-naphthylethyl group). The alkylene group (alkyl chainwithin the arylalkyl group) preferably has 1 to 4 carbon atom, morepreferably 1 or 2, and most preferably 1.

Examples of the cyclic aliphatic hydrocarbon group for R¹⁰¹ includealiphatic hydrocarbon groups containing a ring in the structure thereof.

As examples of the hydrocarbon group containing a ring in the structurethereof, an alicyclic hydrocarbon group (a group in which one hydrogenatom has been removed from an aliphatic hydrocarbon ring), a group inwhich the alicyclic hydrocarbon group is bonded to the terminal of theaforementioned chain-like aliphatic hydrocarbon group, and a group inwhich the alicyclic group is interposed within the aforementioned linearor branched aliphatic hydrocarbon group, can be given.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either a polycyclic group or amonocyclic group. As the monocyclic alicyclic hydrocarbon group, a groupin which one or more hydrogen atoms have been removed from amonocycloalkane is preferable. The monocycloalkane preferably has 3 to 6carbon atoms, and specific examples thereof include cyclopentane andcyclohexane. As the polycyclic alicyclic hydrocarbon group, a group inwhich one or more hydrogen atoms have been removed from apolycycloalkane is preferable, and the polycyclic group preferably has 7to 30 carbon atoms. Among polycycloalkanes, a polycycloalkane having abridged ring polycyclic skeleton, such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclodpdecane, and a polycycloalkanehaving a condensed ring polycyclic skeleton, such as a cyclic grouphaving a steroid skeleton are preferable.

Among these examples, as the cyclic aliphatic hydrocarbon group forR¹⁰¹, a group in which one or more hydrogen atoms have been removed froma monocycloalkane or a polycycloalkane is preferable, a group in whichone or more hydrogen atoms have been removed from a polycycloalkane ismore preferable, an adamantyl group or a norbornyl group is still morepreferable, and an adamantyl group is most preferable.

The linear or branched aliphatic hydrocarbon group which may be bondedto the alicyclic hydrocarbon group preferably has 1 to 10 carbon atoms,more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbonatoms, and most preferably 1 to 3 carbon atoms.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—] and a pentamethylene group [—(CH₂)₅—].

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

The cyclic hydrocarbon group for R¹⁰¹ may contain a hetero atom such asa heterocycle. Specific examples include lactone-containing cyclicgroups represented by the aforementioned general formulae (a2-r-1) to(a2-r-7), the —SO₂— containing cyclic group represented by theaforementioned formulae (a5-r-1) to (a5-r-4), and other heterocyclicgroups represented by chemical formulae (r-hr-1) to (r-hr-16) shownbelow.

As the substituent for the cyclic group for R¹⁰¹, an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup, a carbonyl group, a nitro group or the like can be used.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Example of the aforementioned halogenated alkyl group includes a groupin which a part or all of the hydrogen atoms within an alkyl group of 1to 5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group,an n-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

The carbonyl group as the substituent is a group that substitutes amethylene group (—CH₂—) constituting the cyclic hydrocarbon group.

Chain Alkyl Group which May have a Substituent:

The chain-like alkyl group for R¹⁰¹ may be linear or branched.

The linear alkyl group preferably has 1 to 20 carbon atoms, morepreferably 1 to 15 carbon atoms, and still more preferably 1 to 10carbon atoms. Specific examples include a methyl group, an ethyl group,a propyl group, a butyl group, a pentyl group, a hexyl group, a heptylgroup, an octyl group, a nonyl group, a decyl group, an undecyl group, adodecyl group, a tridecyl group, an isotridecyl group, a tetradecylgroup, a pentadecyl group, a hexadecyl group, an isohexadecyl group, aheptadecyl group, an octadecyl group, a nonadecyl group, an icosylgroup, a henicosyl group and a docosyl group.

The branched alkyl group preferably has 3 to 20 carbon atoms, morepreferably 3 to 15 carbon atoms, and still more preferably 3 to 10carbon atoms. Specific examples include a 1-methylethyl group, a1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a3-methylpentyl group and a 4-methylpentyl group.

Chain Alkenyl Group which May have a Substituent:

The chain-like alkenyl group for R¹⁰¹ may be linear or branched, andpreferably has 2 to 10 carbon atoms, more preferably 2 to 5 carbonatoms, still more preferably 2 to 4 carbon atoms, and most preferably 3carbon atoms. Examples of linear alkenyl groups include a vinyl group, apropenyl group (an allyl group) and a butynyl group. Examples ofbranched alkenyl groups include a 1-methylvinyl group, a 2-methylvinylgroup, a 1-methylpropenyl group and a 2-methylpropenyl group.

Among these examples, as the chain-like alkenyl group, a linear alkenylgroup is preferable, a vinyl group or a propenyl group is morepreferable, and a vinyl group is most preferable.

As the substituent for the chain-like alkyl group or alkenyl group forR¹⁰¹, an alkoxy group, a halogen atom, a halogenated alkyl group, ahydroxyl group, a carbonyl group, a nitro group, an amino group, acyclic group for R¹⁰¹ or the like can be used.

Among these examples, as R¹⁰¹, a cyclic group which may have asubstituent is preferable, and a cyclic hydrocarbon group which may havea substituent is more preferable. Specifically, for example, a phenylgroup, a naphthyl group, a group in which one or more hydrogen atomshave been removed from a polycycloalkane, a lactone-containing cyclicgroup represented by any one of the aforementioned formula (a2-r-1) to(a2-r-7), and an —SO₂— containing cyclic group represented by any one ofthe aforementioned formula (a5-r-1) to (a5-r-4) are preferable.

In formula (b-1), Y¹⁰¹ represents a single bond or a divalent linkinggroup containing an oxygen atom.

In the case where Y¹⁰¹ is a divalent linking group containing an oxygenatom, Y¹⁰¹ may contain an atom other than an oxygen atom. Examples ofatoms other than an oxygen atom include a carbon atom, a hydrogen atom,a sulfur atom and a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom includenon-hydrocarbon, oxygen atom-containing linking groups such as an oxygenatom (an ether bond; —O—), an ester bond (—C(═O)—O—), an oxycarbonylgroup (—O—C(═O)—), an amido bond (—C(═O)—NH—), a carbonyl group(—C(═O)—) and a carbonate bond (—O—C(═O)—O—); and combinations of theaforementioned non-hydrocarbon, hetero atom-containing linking groupswith an alkylene group. Furthermore, the combinations may have asulfonyl group (—SO₂—) bonded thereto. Examples of divalent linkinggroups containing an oxygen atom include linking groups represented bygeneral formulae (y-a1-1) to (y-a1-7) shown below.

In the formulae, V′¹⁰¹ represents a single bond or an alkylene group of1 to 5 carbon atoms; V′¹⁰² represents a divalent saturated hydrocarbongroup of 1 to 30 carbon atoms.

The divalent saturated hydrocarbon group for V′¹⁰² is preferably analkylene group of 1 to 30 carbon atoms, more preferably an alkylenegroup of 1 to 10 carbon atoms, and still more preferably an alkylenegroup of 1 to 5 carbon atoms.

The alkylene group for V′¹⁰¹ and V′¹⁰² may be a linear alkylene group ora branched alkylene group, and a linear alkylene group is preferable.

Specific examples of the alkylene group for V′¹⁰¹ and V′¹⁰² include amethylene group [—CH₂—]; an alkylmethylene group, such as —CH(CH₃)—,—CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and—C(CH₂CH₃)₂—; an ethylene group [—CH₂CH₂—]; an alkylethylene group, suchas —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—; atrimethylene group (n-propylene group) [—CH₂CH₂CH₂—]; analkyltrimethylene group, such as —CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; atetramethylene group [—CH₂CH₂CH₂CH₂—]; an alkyltetramethylene group,such as —CH(CH₃)CH₂CH₂CH₂—, —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylenegroup [—CH₂CH₂CH₂CH₂CH₂—].

Further, part of methylene group within the alkylene group for V′¹⁰¹ andV′¹⁰² may be substituted with a divalent aliphatic cyclic group of 5 to10 carbon atoms. The aliphatic cyclic group is preferably a divalentgroup in which one hydrogen atom has been removed from the cyclicaliphatic hydrocarbon group (monocyclic alicyclic hydrocarbon group orpolycyclic alicyclic hydrocarbon group) for R¹⁰¹ in the aforementionedformula (b-1), and a cyclohexylene group, 1,5-adamantylene group or2,6-adamantylene group is preferable.

Y¹⁰¹ is preferably a divalent linking group containing an ether bond ora divalent linking group containing an ester bond, and groupsrepresented by the aforementioned formulas (y-a1-1) to (y-a1-5) arepreferable.

In formula (b-1), V¹⁰¹ represents a single bond, an alkylene group or afluorinated alkylene group. The alkylene group and the fluorinatedalkylene group for V¹⁰¹ preferably has 1 to 4 carbon atoms. Examples ofthe fluorinated alkylene group for V¹⁰¹ include a group in which part orall of the hydrogen atoms within the alkylene group for V¹⁰¹ have beensubstituted with fluorine. Among these examples, as V¹⁰¹, a single bondor a fluorinated alkylene group of 1 to 4 carbon atoms is preferable.

In formula (b-1), R¹⁰² represents a fluorine atom or a fluorinated alkylgroup of 1 to 5 carbon atoms. R¹⁰² is preferably a fluorine atom or aperfluoroalkyl group of 1 to 5 carbon atoms, and more preferably afluorine atom.

As a specific example of the anion moiety for the component (b-1), inthe case where Y¹⁰¹ a single bond, a fluorinated alkylsulfonate anionsuch as a trifluoromethanesulfonate anion or a perfluorobutanesulfonateanion can be mentioned; and in the case where Y¹⁰¹ represents a divalentlinking group containing an oxygen atom, anions represented by formulae(an-1) to (an-3) shown below can be mentioned.

In the formulae, R″¹⁰¹ represents an aliphatic cyclic group which mayhave a substituent, a group represented by any one of the aforementionedformulas (r-hr-1) to (r-hr-6) or a chain-like alkyl group which may havea substituent; R″¹⁰² represents an aliphatic cyclic group which may havea substituent, a lactone-containing cyclic group represented by any oneof the aforementioned formulae (a2-r-1) to (a2-r-7) or an —SO₂—containing cyclic group represented by any one of the aforementionedformulae (a5-r-1) to (a5-r-4); R″¹⁰³ represents an aromatic cyclic groupwhich may have a substituent, an aliphatic cyclic group which may have asubstituent or a chain-like alkenyl group which may have a substituent;v″ represents an integer of 0 to 3; q″ represents an integer of 1 to 20;t″ represents an integer of 1 to 3; and n″ represents 0 or 1.

As the aliphatic cyclic group for R″¹⁰¹, R″¹⁰² and R″¹⁰³ which may havea substituent, the same groups as the cyclic aliphatic hydrocarbon groupfor R¹⁰¹ described above are preferable. As the substituent, the samegroups as those described above for substituting the cyclic aliphatichydrocarbon group for R¹⁰¹ can be mentioned.

As the aromatic cyclic group for R″¹⁰³ which may have a substituent, thesame groups as the aromatic hydrocarbon group for the cyclic hydrocarbongroup represented by R¹⁰¹ described above are preferable. Thesubstituent is the same as defined for the substituent for the aromatichydrocarbon group represented by R¹¹.

As the chain-like alkyl group for R″¹⁰¹ which may have a substituent,the same groups as those described above for R¹⁰¹ are preferable. As thechain-like alkenyl group for R″¹⁰³ which may have a substituent, thesame groups as those described above for R¹⁰¹ are preferable.

Anion Moiety of Component (b-2)

In formula (b-2), R¹⁰⁴ and R¹⁰⁵ each independently represents a cyclicgroup which may have a substituent, a chain-like alkyl group which mayhave a substituent or a chain-like alkenyl group which may have asubstituent, and is the same as defined for R¹⁰¹ in formula (b-1). R¹⁰⁴and R¹⁰⁵ may be mutually bonded to form a ring.

As R¹⁰⁴ and R¹⁰⁵, a chain-like alkyl group which may have a substituentis preferable, and a linear or branched alkyl group or a linear orbranched fluorinated alkyl group is more preferable.

The chain-like alkyl group preferably has 1 to 10 carbon atoms, morepreferably 1 to 7 carbon atoms, and still more preferably 1 to 3 carbonatoms. The smaller the number of carbon atoms of the chain-like alkylgroup for R¹⁰⁴ and R¹⁰⁵, the more the solubility in a resist solvent isimproved. Further, in the chain-like alkyl group for R¹⁰⁴ and R¹⁰⁵, itis preferable that the number of hydrogen atoms substituted withfluorine atoms is as large as possible because the acid strengthincreases and the transparency to high energy radiation of 200 nm orless or electron beam is improved.

The fluorination ratio of the chain-like alkyl group is preferably from70 to 100%, more preferably from 90 to 100%, and it is particularlydesirable that the chain-like alkyl group be a perfluoroalkyl group inwhich all hydrogen atoms are substituted with fluorine atoms.

In formula (b-2), V¹⁰² and V¹⁰³ each independently represents a singlebond, an alkylene group or a fluorinated alkylene group, and is the sameas defined for V¹⁰¹ in formula (b-1).

In formula (b-2), L¹⁰¹ and L¹⁰² each independently represents a singlebond or an oxygen atom.

Anion Moiety of Component (b-3)

In formula (b-3), R¹⁰⁶ to R¹⁰⁸ each independently represents a cyclicgroup which may have a substituent, a chain-like alkyl group which mayhave a substituent or a chain-like alkenyl group which may have asubstituent, and is the same as defined for R¹⁰¹ in formula (b-1).

L¹⁰³ to L¹⁰⁵ each independently represents a single bond, —CO— or —SO₂—.

{Cation Moiety}

In formulae (b-1), (b-2) and (b-3), m represents an integer of 1 ormore, M′^(m+) represents an onium cation having a valency of m,preferably a sulfonium cation or an iodonium cation, and most preferablyan organic cation represented by any one of the following formulae(ca-1) to (ca-5).

In the formulae, R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² each independentlyrepresents an aryl group, an alkyl group or an alkenyl group, providedthat two of R²⁰¹ to R²⁰³, R²⁰⁶ and R²⁰⁷, or R²¹¹ and R²¹² may bemutually bonded to form a ring with the sulfur atom; R²⁰⁸ and R²⁰⁹ eachindependently represents a hydrogen atom or an alkyl group of 1 to 5carbon atoms; R²¹⁰ represents an aryl group which may have asubstituent, an alkyl group which may have a substituent, an alkenylgroup which may have a substituent, or an —SO₂— containing cyclic groupwhich may have a substituent; L²⁰¹ represents —C(═O)— or —C(═O)—O—; Y²⁰¹each independently represents an arylene group, an alkylene group or analkenylene group; x represents 1 or 2; and W²⁰¹ represents a linkinggroup having a valency of (x+1).

As the aryl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹², an unsubstituted arylgroup of 6 to 20 carbon atoms can be mentioned, and a phenyl group or anaphthyl group is preferable.

The alkyl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² is preferably achain-like or cyclic alkyl group having 1 to 30 carbon atoms.

The alkenyl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² preferably has 2 to 10carbon atoms.

Specific examples of the substituent which R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹²may have include an alkyl group, a halogen atom, a halogenated alkylgroup, a carbonyl group, a cyano group, an amino group, an aryl group,and groups represented by formulae (ca-r-1) to (ca-r-7) shown below.

In the formulae, each R′²⁰¹ independently represents a hydrogen atom, acyclic group which may have a substituent, a chain-like alkyl groupwhich may have a substituent, or a chain-like alkenyl group which mayhave a substituent.

As the cyclic group which may have a substituent, the chain-like alkylgroup which may have a substituent and the chain-like alkenyl groupwhich may have a substituent for R′²⁰¹, the same groups as thosedescribed above for R¹⁰¹ can be mentioned. As the cyclic group which mayhave a substituent and chain-like alkyl group which may have asubstituent, the same groups as those described above for the aciddissociable group represented by the aforementioned formula (a1-r-2) canbe also mentioned.

When R²⁰¹ to R²⁰³, R²⁰⁶, R²⁰⁷, R²¹¹ and R²¹² are mutually bonded to forma ring with the sulfur atom, these groups may be mutually bonded via ahetero atom such as a sulfur atom, an oxygen atom or a nitrogen atom, ora functional group such as a carbonyl group, —SO—, —SO₂—, —SO₃—, —COO—,—CONH— or —N(R_(N))— (wherein R_(N) represents an alkyl group of 1 to 5carbon atoms). The ring containing the sulfur atom in the skeletonthereof is preferably a 3 to 10-membered ring, and most preferably a 5to 7-membered ring. Specific examples of the ring formed include athiophene ring, a thiazole ring, a benzothiophene ring, a thianthrenering, a benzothiophene ring, a dibenzothiophene ring, a 9H-thioxanthenering, a thioxanthone ring, a phenoxathiin ring, a tetrahydrothiopheniumring, and a tetrahydrothiopyranium ring.

R²⁰⁸ and R²⁰⁹ each independently represents a hydrogen atom or an alkylgroup of 1 to 5 carbon atoms, preferably a hydrogen atom or an alkylgroup of 1 to 3 carbon atoms, and when R²⁰⁸ and R²⁰⁹ each represents analkyl group, R²⁰⁸ and R²⁰⁹ may be mutually bonded to form a ring.

R²¹⁰ represents an aryl group which may have a substituent, an alkylgroup which may have a substituent, an alkenyl group which may have asubstituent, or an —SO₂— containing cyclic group which may have asubstituent.

Examples of the aryl group for R²¹⁰ include an unsubstituted aryl groupof 6 to 20 carbon atoms, and a phenyl group or a naphthyl group ispreferable.

As the alkyl group for R²¹⁰, a chain-like or cyclic alkyl group having 1to 30 carbon atoms is preferable.

The alkenyl group for R²¹⁰ preferably has 2 to 10 carbon atoms.

The —SO₂— containing cyclic group for R²¹⁰ which may have a substituentis the same as defined for the —SO₂— containing cyclic group representedby any of the aforementioned general formulae (a5-r-1) to (a5-r-4).Among these examples, the “—SO₂— containing polycyclic group” ispreferable, and a group represented by general formula (a5-r-1) is morepreferable.

In formulae (ca-4) and (ca-5), each Y²⁰¹ independently represents anarylene group, an alkylene group or an alkenylene group.

Examples of the arylene group for Y²⁰¹ include groups in which onehydrogen atom has been removed from an aryl group given as an example ofthe aromatic hydrocarbon group for R¹⁰¹ in the aforementioned formula(b-1).

Examples of the alkylene group and alkenylene group for Y²⁰¹ includegroups in which one hydrogen atom has been removed from the chain-likealkyl group or the chain-like alkenyl group given as an example of R¹⁰¹in the aforementioned formula (b-1).

In formulae (ca-4) and (ca-5), x represents 1 or 2.

W²⁰¹ represents a linking group having a valency of (x+1), i.e., adivalent or trivalent linking group.

As the divalent linking group for W²⁰¹, a divalent hydrocarbon groupwhich may have a substituent is preferable, and as examples thereof, thesame hydrocarbon groups (which may have a substituent) as thosedescribed above for Ya²¹ in the general formula (a2-1) can be mentioned.The divalent linking group for W²⁰¹ may be linear, branched or cyclic,and cyclic is more preferable. Among these, an arylene group having twocarbonyl groups, each bonded to the terminal thereof is preferable.Examples of the arylene group include a phenylene group and anaphthylene group, and a phenylene group is particularly desirable.

As the trivalent linking group for W²⁰¹, a group in which one hydrogenatom has been removed from the aforementioned divalent linking group forW²⁰¹ and a group in which the divalent linking group has been bonded toanother divalent linking group can be mentioned. The trivalent linkinggroup for W²⁰¹ is preferably a group in which 2 carbonyl groups arebonded to an arylene group.

Specific examples of preferable cations represented by formula (ca-1)include cations represented by formulae (ca-1-1) to (ca-1-72) shownbelow.

In the formulae, g1, g2 and g3 represent recurring numbers, wherein g1is an integer of 1 to 5, g2 is an integer of 0 to 20, and g3 is aninteger of 0 to 20.

In the formulae, R″²⁰¹ represents a hydrogen atom or a substituent, andas the substituent, the same groups as those described above forsubstituting R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹² can be mentioned.

Specific examples of preferable cations represented by the formula(ca-2) include a diphenyliodonium cation and abis(4-tert-butylphenyl)iodonium cation.

Specific examples of preferable cations represented by formula (ca-3)include cations represented by formulae (ca-3-1) to (ca-3-6) shownbelow.

Specific examples of preferable cations represented by formula (ca-4)include cations represented by formulae (ca-4-1) and (ca-4-2) shownbelow.

Further, examples of preferable cations represented by formula (ca-5)include cations represented by formulae (ca-5-1) to (ca-5-3) shownbelow.

Among the above examples, as the cation moiety [(M′^(m+))_(1/m)], acation represented by general formula (ca-1) is preferable, and a cationrepresented by any one of formulae (ca-1-1) to (ca-1-72) is morepreferable.

As the component (B), one type of these acid generators may be usedalone, or two or more types may be used in combination.

When the resist composition contains the component (B), the amount ofthe component (B) relative to 100 parts by weight of the component (A)is preferably within a range from 5 to 50 parts by weight, morepreferably from 10 to 40 parts by weight, and still more preferably from10 to 30 parts by weight.

When the amount of the component (B) is within the above-mentionedrange, formation of a resist pattern can be satisfactorily performed.Further, by virtue of the above-mentioned range, when each of thecomponents are dissolved in an organic solvent, a homogeneous solutionmay be more reliably obtained and the storage stability of the resistcomposition becomes satisfactory.

<<Acid Diffusion Control Agent (D)>>

The resist composition according to the present embodiment may includean acid diffusion control agent component (hereafter, sometimes referredto as “component (D)”), in addition to the component (A), or in additionto the component (A) and the component (B). The component (D) functionsas an acid diffusion control agent, i.e., a quencher which traps theacid generated in the resist composition upon exposure.

The component (D) may be a photodecomposable base (D1) (hereafter,referred to as “component (D1)”) which is decomposed upon exposure andthen loses the ability of controlling of acid diffusion, or anitrogen-containing organic compound (D2) (hereafter, referred to as“component (D2)”) which does not fall under the definition of component(D1).

Component (D1)

When a resist pattern is formed using a resist composition containingthe component (D1), the contrast between exposed portions and unexposedportions of the resist film is improved.

The component (D1) is not particularly limited, as long as it isdecomposed upon exposure and then loses the ability of controlling ofacid diffusion. As the component (D1), at least one compound selectedfrom the group consisting of a compound represented by general formula(d1-1) shown below (hereafter, referred to as “component (d1-1)”), acompound represented by general formula (d1-2) shown below (hereafter,referred to as “component (d1-2)”) and a compound represented by generalformula (d1-3) shown below (hereafter, referred to as “component(d1-3)”) is preferably used.

At exposed portions of the resist film, the components (d1-1) to (d1-3)are decomposed and then lose the ability of controlling of aciddiffusion (i.e., basicity), and therefore the components (d1-1) to(d1-3) cannot function as a quencher, whereas at unexposed portions, thecomponents (d1-1) to (d1-3) functions as a quencher.

In the formulae, Rd¹ to Rd⁴ represent a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, provided that,the carbon atom adjacent to the sulfur atom within the Rd² in theformula (d1-2) has no fluorine atom bonded thereto; Yd¹ represents asingle bond or a divalent linking group; m represents an integer of 1 ormore; and each M^(m+) independently represents an organic cation havinga valency of m.

{Component (d1-1)}

Anion Moiety

In formula (d1-1), Rd¹ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and is the samegroups as those defined above for R¹⁰¹ in the aforementioned formula(b-1).

Among these, as the group for Rd¹, an aromatic hydrocarbon group whichmay have a substituent, an aliphatic cyclic group which may have asubstituent and a chain-like alkyl group which may have a substituentare preferable. Examples of the substituent for these groups include ahydroxy group, an oxo group, an alkyl group, an aryl group, a fluorineatom, a fluorinated alkyl group, a lactone-containing cyclic grouprepresented by any one of the aforementioned formulae (a2-r-1) to(a2-r-7), an ether bond, an ester bond, and a combination thereof. Inthe case where an ether bond or an ester bond is included as thesubstituent, the substituent may be bonded via an alkylene group, and alinking group represented by any one of the aforementioned formulae(y-a1-1) to (y-a1-5) is preferable as the substituent.

The aromatic hydrocarbon group is preferably a phenyl group or anaphthyl group.

Examples of the aliphatic cyclic group include groups in which one ormore hydrogen atoms have been removed from a polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane.

The chain-like alkyl group preferably has 1 to 10 carbon atoms, andspecific examples thereof include a linear alkyl group such as a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a nonyl or a decyl group,and a branched alkyl group such as a 1-methylethyl group, a1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a3-methylpentyl group or a 4-methylpentyl group.

In the case where the chain-like alkyl group is a fluorinated alkylgroup having a fluorine atom or a fluorinated alkyl group, thefluorinated alkyl group preferably has 1 to 11 carbon atoms, morepreferably 1 to 8 carbon atoms, and still more preferably 1 to 4 carbonatoms. The fluorinated alkyl group may contain an atom other thanfluorine. Examples of the atom other than fluorine include an oxygenatom, a sulfur atom and a nitrogen atom.

As Rd¹, a fluorinated alkyl group in which part or all of the hydrogenatoms constituting a linear alkyl group have been substituted withfluorine atom(s) is preferable, and a fluorinated alkyl group in whichall of the hydrogen atoms constituting a linear alkyl group have beensubstituted with fluorine atoms (i.e., a linear perfluoroalkyl group) isparticularly desirable.

Specific examples of preferable anion moieties for the component (d1-1)are shown below.

Cation Moiety

In formula (d1-1), M^(m+) represents an organic cation having a valencyof m. As the organic cation for M^(m+), for example, the same cationmoieties as those represented by the aforementioned formulae (ca-1) to(ca-5) are preferable, cation moieties represented by the aforementionedgeneral formulae (ca-1) is preferable, and cation moieties representedby the aforementioned formulae (ca-1-1) to (ca-1-72) are still morepreferable.

As the component (d1-1), one type of compound may be used, or two ormore types of compounds may be used in combination.

{Component (d1-2)}

Anion Moiety

In formula (d1-2), Rd² represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and is the samegroups as those defined above for R¹⁰¹ in the aforementioned formula(b-1).

provided that, the carbon atom adjacent to the sulfur atom within Rd²group has no fluorine atom bonded thereto (i.e., the carbon atomadjacent to the sulfur atom within Rd² group does not substituted with afluorine atom). As a result, the anion of the component (d1-2) becomesan appropriately weak acid anion, thereby improving the quenchingability of the component (D).

As Rd², a chain-like alkyl group which may have a substituent or analiphatic cyclic group which may have a substituent is preferable. Thechain-like alkyl group preferably has 1 to 10 carbon atoms, and morepreferably 3 to 10 carbon atoms. As the aliphatic cyclic group, a groupin which one or more hydrogen atoms have been removed from adamantane,norbornane, isobornane, tricyclodecane, tetracyclododecane or camphor(which may have a substituent) is more preferable.

The hydrocarbon group for Rd² may have a substituent. As thesubstituent, the same groups as those described above for substitutingthe hydrocarbon group (e.g., aromatic hydrocarbon group, aliphaticcyclic group, chain-like alkyl group) for Rd¹ in the formula (d1-1) canbe mentioned.

Specific examples of preferable anion moieties for the component (d1-2)are shown below.

Cation Moiety

In formula (d1-2), M^(m+) is an organic cation having a valency of m,and is the same as defined for M^(m+) in the aforementioned formula(d1-1).

As the component (d1-2), one type of compound may be used, or two ormore types of compounds may be used in combination.

{Component (d1-3)}

Anion Moiety

In formula (d1-3), Rd³ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and is the samegroups as those defined above for R¹⁰¹ in the aforementioned formula(b-1), and a cyclic group containing a fluorine atom, a chain-like alkylgroup or a chain-like alkenyl group is preferable. Among these, afluorinated alkyl group is preferable, and more preferably the samefluorinated alkyl groups as those described above for Rd¹.

In formula (d1-3), Rd⁴ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and is the samegroups as those defined above for R¹⁰¹ in the aforementioned formula(b-1).

Among these, an alkyl group which may have substituent, an alkoxy groupwhich may have substituent, an alkenyl group which may have substituentor a cyclic group which may have substituent is preferable.

The alkyl group for Rd⁴ is preferably a linear or branched alkyl groupof 1 to 5 carbon atoms, and specific examples include a methyl group, anethyl group, a propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a tert-butyl group, a pentyl group, an isopentyl group,and a neopentyl group. Part of the hydrogen atoms within the alkyl groupfor Rd⁴ may be substituted with a hydroxy group, a cyano group or thelike.

The alkoxy group for Rd⁴ is preferably an alkoxy group of 1 to 5 carbonatoms, and specific examples thereof include a methoxy group, an ethoxygroup, an n-propoxy group, an iso-propoxy group, an n-butoxy group and atert-butoxy group. Among these, a methoxy group and an ethoxy group arepreferable.

As the alkenyl group for Rd⁴, the same groups as those described abovefor R¹⁰¹ in the aforementioned formula (b-1) can be mentioned, and avinyl group, a propenyl group (an allyl group), a 1-methylpropenyl groupand a 2-methylpropenyl group are preferable. These groups may have analkyl group of 1 to 5 carbon atoms or a halogenated alkyl group of 1 to5 carbon atoms as a substituent.

As the cyclic group for Rd⁴, the same groups as those described abovefor R¹⁰¹ in the aforementioned formula (b-1) can be mentioned. Amongthese, as the cyclic group, an alicyclic group (e.g., a group in whichone or more hydrogen atoms have been removed from a cycloalkane such ascyclopentane, cyclohexane, adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane) or an aromatic group (e.g., aphenyl group or a naphthyl group) is preferable. When Rd⁴ is analicyclic group, the resist composition can be satisfactorily dissolvedin an organic solvent, thereby improving the lithography properties.Alternatively, when Rd⁴ is an aromatic group, the resist compositionexhibits an excellent photoabsorption efficiency in a lithographyprocess using EUV or the like as the exposure source, thereby resultingin the improvement of the sensitivity and the lithography properties.

In formula (d1-3), Yd¹ represents a single bond or a divalent linkinggroup.

The divalent linking group for Yd¹ is not particularly limited, andexamples thereof include a divalent hydrocarbon group (aliphatichydrocarbon group, or aromatic hydrocarbon group) which may have asubstituent and a divalent linking group containing a hetero atom. Thedivalent linking groups are the same as defined for the divalenthydrocarbon group which may have a substituent and the divalent linkinggroup containing a hetero atom explained above as the divalent linkinggroup for Ya²¹ in the aforementioned formula (a2-1).

As Yd¹, a carbonyl group, an ester bond, an amide bond, an alkylenegroup or a combination of these is preferable. As the alkylene group, alinear or branched alkylene group is more preferable, and a methylenegroup or an ethylene group is still more preferable.

Specific examples of preferable anion moieties for the component (d1-3)are shown below.

Cation Moiety

In formula (d1-3), M^(m+) is an organic cation having a valency of m,and is the same as defined for M^(m+) in the aforementioned formula(d1-1).

As the component (d1-3), one type of compound may be used, or two ormore types of compounds may be used in combination.

As the component (D1), one type of the aforementioned components (d1-1)to (d1-3), or at least two types of the aforementioned components (d1-1)to (d1-3) can be used in combination.

When the resist composition contains the component (D1), the amount ofthe component (D1) relative to 100 parts by weight of the component (A)is preferably within a range from 0.5 to 10 parts by weight, morepreferably from 0.5 to 8 parts by weight, and still more preferably from1 to 8 parts by weight.

When the amount of the component (D1) is at least as large as the lowerlimit of the above-mentioned range, excellent lithography properties andexcellent resist pattern shape can be more reliably obtained. On theother hand, when the amount of the component (D1) is no more than theupper limit of the above-mentioned range, sensitivity can be maintainedat a satisfactory level, and through-put becomes excellent.

Production Method of Component (D1):

The production methods of the components (d1-1) and (d1-2) are notparticularly limited, and the components (d1-1) and (d1-2) can beproduced by conventional methods.

Further, the production method of the component (d1-3) is notparticularly limited, and the component (d1-3) can be produced in thesame manner as disclosed in US2012-0149916.

Component (D2)

The acid diffusion control component may contain a nitrogen-containingorganic compound (D2) (hereafter, referred to as component (D2)) whichdoes not fall under the definition of component (D1).

The component (D2) is not particularly limited, as long as it functionsas an acid diffusion control agent, and does not fall under thedefinition of the component (D1). As the component (D2), any of theconventionally known compounds may be selected for use. Among these, analiphatic amine is preferable, and a secondary aliphatic amine ortertiary aliphatic amine is more preferable.

An aliphatic amine is an amine having one or more aliphatic groups, andthe aliphatic groups preferably have 1 to 12 carbon atoms.

Examples of these aliphatic amines include amines in which at least onehydrogen atom of ammonia (NH₃) has been substituted with an alkyl groupor hydroxyalkyl group of no more than 12 carbon atoms (i.e., alkylaminesor alkylalcoholamines), and cyclic amines.

Specific examples of alkylamines and alkylalcoholamines includemonoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine,n-nonylamine, and n-decylamine; dialkylamines such as diethylamine,di-n-propylamine, di-n-heptylamine, di-n-octylamine, anddicyclohexylamine; trialkylamines such as trimethylamine, triethylamine,tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine,tri-n-pentylamine, tri-n-heptylamine, tri-n-octylamine,tri-n-nonylamine, tri-n-decylamine, and tri-n-dodecylamine; and alkylalcohol amines such as diethanolamine, triethanolamine,diisopropanolamine, triisopropanolamine, di-n-octanolamine, andtri-n-octanolamine. Among these, trialkylamines of 5 to 10 carbon atomsare preferable, and tri-n-pentylamine and tri-n-octylamine areparticularly desirable.

Examples of the cyclic amine include heterocyclic compounds containing anitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidine,and piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1,5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

Examples of other aliphatic amines includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine and triethanolaminetriacetate, and triethanolamine triacetate is preferable.

Further, as the component (D2), an aromatic amine may be used.

Examples of aromatic amines include 4-dimethylaminopyridine, pyrrole,indole, pyrazole, imidazole and derivatives thereof, as well astribenzylamine, 2,6-diisopropylaniline andN-tert-butoxycarbonylpyrrolidine.

As the component (D2), one type of compound may be used alone, or two ormore types may be used in combination.

When the resist composition contains the component (D2), the amount ofthe component (D2) is typically used in an amount within a range from0.01 to 5 parts by weight, relative to 100 parts by weight of thecomponent (A). When the amount of the component (D) is within theabove-mentioned range, the shape of the resist pattern and the postexposure stability of the latent image formed by the pattern-wiseexposure of the resist layer are improved.

<<At Least One Compound (E) Selected from the Group Consisting of anOrganic Carboxylic Acid, or a Phosphorus Oxo Acid or DerivativeThereof>>

In the resist composition of the present embodiment, for preventing anydeterioration in sensitivity, and improving the resist pattern shape andthe post exposure stability of the latent image formed by thepattern-wise exposure of the resist layer, at least one compound (E)(hereafter referred to as the component (E)) selected from the groupconsisting of an organic carboxylic acid, or a phosphorus oxo acid orderivative thereof may be added.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids include phosphoric acid, phosphonicacid and phosphinic acid. Among these, phosphonic acid is particularlydesirable.

Examples of oxo acid derivatives include esters in which a hydrogen atomwithin the above-mentioned oxo acids is substituted with a hydrocarbongroup. Examples of the hydrocarbon group include an alkyl group of 1 to5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esterssuch as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonicacid, diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid estersand phenylphosphinic acid.

As the component (E), one type may be used alone, or two or more typesmay be used in combination.

When the resist composition contains the component (E), the amount ofthe component (E) is typically used in an amount within a range from0.01 to 5 parts by weight, relative to 100 parts by weight of thecomponent (A).

<<Fluorine Additive (F)>>

In the present embodiment, the resist composition may further include afluorine additive (hereafter, referred to as “component (F)”) forimparting water repellency to the resist film.

As the component (F), for example, a fluorine-containing polymericcompound described in Japanese Unexamined Patent Application, FirstPublication No. 2010-002870, Japanese Unexamined Patent Application,First Publication No. 2010-032994, Japanese Unexamined PatentApplication, First Publication No. 2010-277043, Japanese UnexaminedPatent Application, First Publication No. 2011-13569, and JapaneseUnexamined Patent Application, First Publication No. 2011-128226 can beused.

Specific examples of the component (F) include polymers having astructural unit (f1) represented by general formula (f1-1) shown below.As the polymer, a polymer (homopolymer) consisting of a structural unit(f1) represented by formula (f1-1) shown below; a copolymer of thestructural unit (f1) and a structural unit (a1) containing an aciddecomposable group that exhibits increased polarity by the action ofacid; and a copolymer of the structural unit (f1), a structural unitderived from acrylic acid or methacrylic acid and the structural unit(a1) are preferable. As the structural unit (a1) to be copolymerizedwith the structural unit (f1), a structural unit derived from1-ethyl-1-cyclooctyl(meth)acrylate or a structural unit derived from1-methyl-1-adamantyl(meth)acrylate is preferable.

In the formula, R is the same as defined above; Rf¹⁰² and Rf¹⁰³ eachindependently represents a hydrogen atom, a halogen atom, an alkyl groupof 1 to 5 carbon atoms, or a halogenated alkyl group of 1 to 5 carbonatoms, provided that Rf¹⁰² and Rf¹⁰³ may be the same or different; nf¹represents an integer of 1 to 5; and Rf¹⁰¹ represents an organic groupcontaining a fluorine atom.

In formula (f1-1), R bonded to the carbon atom on the α-position is thesame as defined above. As R, a hydrogen atom or a methyl group ispreferable.

In formula (f1-1), examples of the halogen atom for Rf¹⁰² and Rf¹⁰³include a fluorine atom, a chlorine atom, a bromine atom and an iodineatom, and a fluorine atom is particularly desirable. Examples of thealkyl group of 1 to 5 carbon atoms for Rf¹⁰² and Rf¹⁰³ include the samealkyl group of 1 to 5 carbon atoms as those described above for R, and amethyl group or an ethyl group is preferable. Specific examples of thehalogenated alkyl group of 1 to 5 carbon atoms represented by Rf¹⁰² orRf¹⁰³ include groups in which part or all of the hydrogen atoms of theaforementioned alkyl groups of 1 to 5 carbon atoms have been substitutedwith halogen atoms.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom, and a fluorine atom is particularlydesirable. Among these examples, as Rf¹⁰² and Rf¹⁰³, a hydrogen atom, afluorine atom or an alkyl group of 1 to 5 carbon atoms is preferable,and a hydrogen atom, a fluorine atom, a methyl group or an ethyl groupis more preferable.

In formula (f1-1), nf¹ represents an integer of 1 to 5, preferably aninteger of 1 to 3, and more preferably 1 or 2.

In formula (f1-1), Rf¹⁰¹ represents an organic group containing afluorine atom, and is preferably a hydrocarbon group containing afluorine atom.

The hydrocarbon group containing a fluorine atom may be linear, branchedor cyclic, and preferably has 1 to 20 carbon atoms, more preferably 1 to15 carbon atoms, and most preferably 1 to 10 carbon atoms.

It is preferable that the hydrocarbon group having a fluorine atom has25% or more of the hydrogen atoms within the hydrocarbon groupfluorinated, more preferably 50% or more, and most preferably 60% ormore, as the hydrophobicity of the resist film during immersion exposureis enhanced.

Among these, as Rf¹⁰¹, a fluorinated hydrocarbon group of 1 to 6 carbonatoms is preferable, and a trifluoromethyl group, —CH₂—CF₃,—CH₂—CF₂—CF₃, —CH(CF₃)₂, —CH₂—CH₂—CF₃, and —CH₂—CH₂—CF₂—CF₂—CF₂—CF₃ aremost preferable.

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component (F)is preferably 1,000 to 50,000, more preferably 5,000 to 40,000, and mostpreferably 10,000 to 30,000. When the Mw of the component (F) is no morethan the upper limit of the above-mentioned range, the resistcomposition exhibits a satisfactory solubility in a resist solvent. Onthe other hand, when the Mw is at least as large as the lower limit ofthe above-mentioned range, dry etching resistance and thecross-sectional shape of the resist pattern becomes satisfactory.

Further, the dispersity (Mw/Mn) of the component (F) is preferably 1.0to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5.

As the component (F), one type may be used alone, or two or more typesmay be used in combination.

When the resist composition contains the component (F), the component(F) is used in an amount within a range from 0.5 to 10 parts by weight,relative to 100 parts by weight of the component (A).

If desired, other miscible additives can also be added to the resistcomposition of the present invention. Examples of such miscibleadditives include additive resins for improving the performance of theresist film, dissolution inhibitors, plasticizers, stabilizers,colorants, halation prevention agents, and dyes.

<<Organic Solvent (S)>>

The resist composition of the present embodiment may be prepared bydissolving the resist materials for the resist composition in an organicsolvent (hereafter, referred to as “component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a homogeneous solution, and any organicsolvent can be appropriately selected from those which have beenconventionally known as solvents for a chemically amplified resistcomposition.

Examples of the component (S) include lactones such as γ-butyrolactone;ketones such as acetone, methyl ethyl ketone, cyclohexanone,methyl-n-pentyl ketone, methyl isopentyl ketone, and 2-heptanone;polyhydric alcohols, such as ethylene glycol, diethylene glycol,propylene glycol and dipropylene glycol; compounds having an ester bond,such as ethylene glycol monoacetate, diethylene glycol monoacetate,propylene glycol monoacetate, and dipropylene glycol monoacetate;polyhydric alcohol derivatives including compounds having an ether bond,such as a monoalkylether (e.g., monomethylether, monoethylether,monopropylether or monobutylether) or monophenylether of any of thesepolyhydric alcohols or compounds having an ester bond (among these,propylene glycol monomethyl ether acetate (PGMEA) and propylene glycolmonomethyl ether (PGME) are preferable); cyclic ethers such as dioxane;esters such as methyl lactate, ethyl lactate (EL), methyl acetate, ethylacetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; aromatic organic solventssuch as anisole, ethylbenzylether, cresylmethylether, diphenylether,dibenzylether, phenetole, butylphenylether, ethylbenzene,diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymeneand mesitylene; and dimethylsulfoxide (DMSO).

The component (S) can be used individually, or in combination as a mixedsolvent.

Among these, PGMEA, PGME, γ-butyrolactone, EL and cyclohexanone arepreferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1, more preferably from 2:8 to8:2.

Specifically, when EL or cyclohexanone is mixed as the polar solvent,the PGMEA:EL or cyclohexanone weight ratio is preferably from 1:9 to9:1, and more preferably from 2:8 to 8:2. Alternatively, when PGME ismixed as the polar solvent, the PGMEA:PGME weight ratio is preferablyfrom 1:9 to 9:1, more preferably from 2:8 to 8:2, and still morepreferably 3:7 to 7:3. Furthermore, a mixed solvent of PGMEA, PGME andcyclohexanone is also preferable.

Further, as the component (S), a mixed solvent of at least one of PGMEAand EL with γ-butyrolactone is also preferable. The mixing ratio(former:latter) of such a mixed solvent is preferably from 70:30 to95:5.

The amount of the component (S) is not particularly limited, and isappropriately adjusted to a concentration which enables coating of acoating solution to a substrate. In general, the component (S) is usedin an amount such that the solid content of the resist compositionbecomes within the range from 1 to 20% by weight, and preferably from 2to 15% by weight.

As described above, the resist composition of the present embodimentemploys a resin component (A1) including a structural unit having aspecific structure, namely, a structural unit (a0) represented bygeneral formula (a0-1).

In the formation of a resist pattern, the tertiary carbonatom-containing group protecting the oxy group (—O—) side of thecarbonyloxy group [—C(═O)—O—] in the structural unit (a0) has a highreaction efficiency to acid, and is reliably dissociated. Therefore, byusing a resist composition containing the component (A1), bothsensitivity and resolution can be improved. In addition, by virtue ofthe tertiary carbon atom-containing group in the structural unit (a0)containing an electron-withdrawing group as a substituent,hydrophilicity of the resist composition is enhanced. Therefore, duringdeveloping, solubility of the resist composition in a developingsolution is improved, and an excellent development contrast can bereliably obtained. As a result, the roughness of the pattern can bereduced.

Thus, by the resist composition of the present embodiment, sensitivitycan be enhanced in the formation of a resist pattern, and it becomespossible to form a resist pattern exhibiting excellent lithographyproperties (resolution, reduction of roughness, and the like).

Furthermore, in the resist composition of the present embodiment, byusing a resin component (A1) having a structural unit (a0) and astructural unit (a10), particularly in the formation of a resist patternusing EUV (extreme ultraviolet) or EB (electron beam) as an exposuresource, both high sensitivity and excellent lithography properties(resolution, reduction of roughness, and the like) can be satisfied.

(Method of Forming a Resist Pattern)

The method of forming a resist pattern according to the presentembodiment includes: forming a resist film on a substrate using a resistcomposition of the aforementioned embodiment; conducting exposure of theresist film; and developing the resist film to form a resist pattern.

The method for forming a resist pattern according to the presentembodiment can be performed, for example, as follows.

Firstly, a resist composition of the first aspect is applied to asubstrate using a spinner or the like, and a bake treatment (postapplied bake (PAB)) is conducted at a temperature of 80 to 150° C. for40 to 120 seconds, preferably 60 to 90 seconds, to form a resist film.

Following selective exposure of the thus formed resist film, either byexposure through a mask having a predetermined pattern formed thereon(mask pattern) using an exposure apparatus such an ArF exposureapparatus, an electron beam lithography apparatus or an EUV exposureapparatus, or by patterning via direct irradiation with an electron beamwithout using a mask pattern, baking treatment (post exposure baking(PEB)) is conducted under temperature conditions of 80 to 150° C. for 40to 120 seconds, and preferably 60 to 90 seconds.

Next, the resist film is subjected to a developing treatment. Thedeveloping treatment is conducted using an alkali developing solution inthe case of an alkali developing process, and a developing solutioncontaining an organic solvent (organic developing solution) in the caseof a solvent developing process.

After the developing treatment, it is preferable to conduct a rinsetreatment. The rinse treatment is preferably conducted using pure waterin the case of an alkali developing process, and a rinse solutioncontaining an organic solvent in the case of a solvent developingprocess.

In the case of a solvent developing process, after the developingtreatment or the rinsing, the developing solution or the rinse liquidremaining on the pattern can be removed by a treatment using asupercritical fluid.

After the developing treatment or the rinse treatment, drying isconducted. If desired, bake treatment (post bake) can be conductedfollowing the developing.

In this manner, a resist pattern can be formed.

The substrate is not specifically limited and a conventionally knownsubstrate can be used. For example, substrates for electroniccomponents, and such substrates having wiring patterns formed thereoncan be used. Specific examples of the material of the substrate includemetals such as silicon wafer, copper, chromium, iron and aluminum; andglass. Suitable materials for the wiring pattern include copper,aluminum, nickel, and gold.

Further, as the substrate, any one of the above-mentioned substratesprovided with an inorganic and/or organic film on the surface thereofmay be used. As the inorganic film, an inorganic antireflection film(inorganic BARC) can be used. As the organic film, an organicantireflection film (organic BARC) and an organic film such as alower-layer organic film used in a multilayer resist method can be used.

Here, a “multilayer resist method” is method in which at least one layerof an organic film (lower-layer organic film) and at least one layer ofa resist film (upper resist film) are provided on a substrate, and aresist pattern formed on the upper resist film is used as a mask toconduct patterning of the lower-layer organic film. This method isconsidered as being capable of forming a pattern with a high aspectratio. More specifically, in the multilayer resist method, a desiredthickness can be ensured by the lower-layer organic film, and as aresult, the thickness of the resist film can be reduced, and anextremely fine pattern with a high aspect ratio can be formed.

The multilayer resist method is broadly classified into a method inwhich a double-layer structure consisting of an upper-layer resist filmand a lower-layer organic film is formed (double-layer resist method),and a method in which a multilayer structure having at least threelayers consisting of an upper-layer resist film, a lower-layer organicfilm and at least one intermediate layer (thin metal film or the like)provided between the upper-layer resist film and the lower-layer organicfilm (triple-layer resist method).

The wavelength to be used for exposure is not particularly limited andthe exposure can be conducted using radiation such as ArF excimer laser,KrF excimer laser, F₂ excimer laser, extreme ultraviolet rays (EUV),vacuum ultraviolet rays (VUV), electron beam (EB), X-rays, and softX-rays. The resist composition is effective to KrF excimer laser, ArFexcimer laser, EB and EUV, and more effective to ArF excimer laser, EBand EUV, and most effective to EB and EUV.

The exposure of the resist film can be either a general exposure (dryexposure) conducted in air or an inert gas such as nitrogen, orimmersion exposure (immersion lithography).

In immersion lithography, the region between the resist film and thelens at the lowermost point of the exposure apparatus is pre-filled witha solvent (immersion medium) that has a larger refractive index than therefractive index of air, and the exposure (immersion exposure) isconducted in this state.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist film to be exposed. The refractive index of the immersion mediumis not particularly limited as long as it satisfies the above-mentionedrequirements.

Examples of this immersion medium which exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist film include water, fluorine-based inertliquids, silicon-based solvents and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, which have a boiling pointwithin a range from 70 to 180° C. and preferably from 80 to 160° C. Afluorine-based inert liquid having a boiling point within theabove-mentioned range is advantageous in that the removal of theimmersion medium after the exposure can be conducted by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly desirable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point 174° C.).

As the immersion medium, water is preferable in terms of cost, safety,environment and versatility.

As an example of the alkali developing solution used in an alkalideveloping process, a 0.1 to 10% by weight aqueous solution oftetramethylammonium hydroxide (TMAH) can be given.

As the organic solvent contained in the organic developing solution usedin a solvent developing process, any of the conventional organicsolvents can be used which are capable of dissolving the component (A)(prior to exposure). Specific examples of the organic solvent includepolar solvents such as ketone solvents, ester solvents, alcoholsolvents, nitrile solvents, amide solvents and ether solvents, andhydrocarbon solvents.

A ketone solvent is an organic solvent containing C—C(═O)—C within thestructure thereof. An ester solvent is an organic solvent containingC—C(═O)—O—C within the structure thereof. An alcohol solvent is anorganic solvent containing an alcoholic hydroxy group in the structurethereof. An “alcoholic hydroxy group” refers to a hydroxy group bondedto a carbon atom of an aliphatic hydrocarbon group. A nitrile solvent isan organic solvent containing a nitrile group in the structure thereof.An amide solvent is an organic solvent containing an amide group withinthe structure thereof. An ether solvent is an organic solvent containingC—O—C within the structure thereof.

Some organic solvents have a plurality of the functional groups whichcharacterizes the aforementioned solvents within the structure thereof.In such a case, the organic solvent can be classified as any type of thesolvent having the characteristic functional group. For example,diethyleneglycol monomethylether can be classified as either an alcoholsolvent or an ether solvent.

A hydrocarbon solvent consists of a hydrocarbon which may behalogenated, and does not have any substituent other than a halogenatom. Examples of the halogen atom include a fluorine atom, a chlorineatom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

As the organic solvent contained in the organic developing solution,among these, a polar solvent is preferable, and ketone solvents, estersolvents and nitrile solvents are preferable.

Examples of ketone solvents include 1-octanone, 2-octanone, 1-nonanone,2-nonanone, acetone, 4-heptanone, 1-hexanone, 2-hexanone, diisobutylketone, cyclohexanone, methylcyclohexanone, phenylacetone, methyl ethylketone, methyl isobutyl ketone, acetylacetone, acetonylacetone, ionone,diacetonylalcohol, acetylcarbinol, acetophenone, methyl naphthyl ketone,isophorone, propylenecarbonate, γ-butyrolactone and methyl amyl ketone(2-heptanone). Among these examples, as a ketone solvent, methyl amylketone (2-heptanone) is preferable.

Examples of ester solvents include methyl acetate, butyl acetate, ethylacetate, isopropyl acetate, amyl acetate, isoamyl acetate, ethylmethoxyacetate, ethyl ethoxyacetate, propylene glycol monomethyl etheracetate, ethylene glycol monoethyl ether acetate, ethylene glycolmonopropyl ether acetate, ethylene glycol monobutyl ether acetate,ethylene glycol monophenyl ether acetate, diethylene glycol monomethylether acetate, diethylene glycol monopropyl ether acetate, diethyleneglycol monoethyl ether acetate, diethylene glycol monophenyl etheracetate, diethylene glycol monobutyl ether acetate, diethylene glycolmonoethyl ether acetate, 2-methoxybutyl acetate, 3-methoxybutyl acetate,4-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate,3-ethyl-3-methoxybutyl acetate, propylene glycol monomethyl etheracetate, propylene glycol monoethyl ether acetate, propylene glycolmonopropyl ether acetate, 2-ethoxybutyl acetate, 4-ethoxybutyl acetate,4-propoxybutyl acetate, 2-methoxypentyl acetate, 3-methoxypentylacetate, 4-methoxypentyl acetate, 2-methyl-3-methoxypentyl acetate,3-methyl-3-methoxypentyl acetate, 3-methyl-4-methoxypentyl acetate,4-methyl-4-methoxypentyl acetate, propylene glycol diacetate, methylformate, ethyl formate, butyl formate, propyl formate, ethyl lactate,butyl lactate, propyl lactate, ethyl carbonate, propyl carbonate, butylcarbonate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, butylpyruvate, methyl acetoacetate, ethyl acetoacetate, methyl propionate,ethyl propionate, propyl propionate, isopropyl propionate, methyl2-hydroxypropionate, ethyl 2-hydroxypropionate,methyl-3-methoxypropionate, ethyl-3-methoxypropionate,ethyl-3-ethoxypropionate and propyl-3-methoxypropionate. Among theseexamples, as an ester solvent, butyl acetate is preferable.

Examples of nitrile solvents include acetonitrile, propionitrile,valeronitrile, butyronitrile and the like.

If desired, the organic developing solution may have a conventionaladditive blended. Examples of the additive include surfactants. Thesurfactant is not particularly limited, and for example, an ionic ornon-ionic fluorine and/or silicon surfactant can be used.

As the surfactant, a non-ionic surfactant is preferable, and a non-ionicfluorine surfactant or a non-ionic silicon surfactant is morepreferable.

When a surfactant is added, the amount thereof based on the total amountof the organic developing solution is generally 0.001 to 5% by weight,preferably 0.005 to 2% by weight, and more preferably 0.01 to 0.5% byweight.

The developing treatment can be performed by a conventional developingmethod. Examples thereof include a method in which the substrate isimmersed in the developing solution for a predetermined time (a dipmethod), a method in which the developing solution is cast up on thesurface of the substrate by surface tension and maintained for apredetermined period (a puddle method), a method in which the developingsolution is sprayed onto the surface of the substrate (spray method),and a method in which the developing solution is continuously ejectedfrom a developing solution ejecting nozzle while scanning at a constantrate to apply the developing solution to the substrate while rotatingthe substrate at a constant rate (dynamic dispense method).

As the organic solvent contained in the rinse liquid used in the rinsetreatment after the developing treatment in the case of a solventdeveloping process, any of the aforementioned organic solvents containedin the organic developing solution can be used which hardly dissolvesthe resist pattern. In general, at least one solvent selected from thegroup consisting of hydrocarbon solvents, ketone solvents, estersolvents, alcohol solvents, amide solvents and ether solvents is used.Among these, at least one solvent selected from the group consisting ofhydrocarbon solvents, ketone solvents, ester solvents, alcohol solventsand amide solvents is preferable, more preferably at least one solventselected from the group consisting of alcohol solvents and estersolvents, and an alcohol solvent is particularly desirable.

The alcohol solvent used for the rinse liquid is preferably a monohydricalcohol of 6 to 8 carbon atoms, and the monohydric alcohol may belinear, branched or cyclic. Specific examples thereof include 1-hexanol,1-heptanol, 1-octanol, 2-hexanol, 2-heptanol, 2-octanol, 3-hexanol,3-heptanol, 3-octanol, 4-octanol and benzyl alcohol. Among these,1-hexanol, 2-heptanol and 2-hexanol are preferable, and 1 hexanol and2-hexanol are more preferable.

As the organic solvent, one kind of solvent may be used alone, or two ormore kinds of solvents may be used in combination. Further, an organicsolvent other than the aforementioned examples or water may be mixedtogether. However, in consideration of the development characteristics,the amount of water within the rinse liquid, based on the total amountof the rinse liquid is preferably 30% by weight or less, more preferably10% by weight or less, still more preferably 5% by weight or less, andmost preferably 3% by weight or less.

If desired, the rinse solution may have a conventional additive blended.Examples of the additive include surfactants. Examples of the additiveinclude surfactants. As the surfactant, the same surfactants as thosedescribed above can be mentioned, a non-ionic surfactant is preferable,and a non-ionic fluorine surfactant or a non-ionic silicon surfactant ismore preferable.

When a surfactant is added, the amount thereof based on the total amountof the rinse liquid is generally 0.001 to 5% by weight, preferably 0.005to 2% by weight, and more preferably 0.01 to 0.5% by weight.

The rinse treatment using a rinse liquid (washing treatment) can beconducted by a conventional rinse method. Examples of the rinse methodinclude a method in which the rinse liquid is continuously applied tothe substrate while rotating it at a constant rate (rotational coatingmethod), a method in which the substrate is immersed in the rinse liquidfor a predetermined time (dip method), and a method in which the rinseliquid is sprayed onto the surface of the substrate (spray method).

In the method of forming a resist pattern according to the presentembodiment, since the resist composition according to the firstembodiment described above is used, sensitivity can be enhanced in theformation of a resist pattern. In addition, by the method of forming aresist pattern according to the present embodiment, lithographyproperties (resolution, reduction of roughness, and the like) can beimproved, and resolution can be enhanced. As a result, it becomespossible to form a resist pattern having a good shape.

(Polymeric Compound)

The polymeric compound of the present embodiment has a structural unit(a0) derived from a compound represented by general formula (a0-1) shownbelow.

In the formula, W represents a polymerizable group-containing group;Ra⁰¹ represents an alkyl group or an aromatic heterocyclic groupcontaining an oxygen atom or a sulfur atom; in the case where Ra⁰¹ is anaromatic heterocyclic group containing an oxygen atom or a sulfur atom,Ra⁰² is a group which forms an aliphatic cyclic group together with thetertiary carbon atom (*C) to which Ra⁰¹ is bonded, provided that thealiphatic cyclic group contains an electron-withdrawing group as asubstituent; and in the case where Ra⁰¹ is an alkyl group, Ra⁰² is agroup in which an aliphatic cyclic group forms a condensed ring togetherwith an aromatic heterocyclic group containing an oxygen atom or asulfur atom, provided that the aliphatic cyclic group is formed togetherwith the tertiary carbon atom (*C) to which Ra⁰¹ is bonded, and thealiphatic cyclic group contains an electron-withdrawing group as asubstituent.

In the case where the polymeric compound of the present embodiment isapplied to, for example, a base resin for a resist composition, theamount of the structural unit (a0) based on the combined total of allstructural units constituting the polymeric compound is preferably 20 to80 mol %, more preferably 30 to 75 mol %, and still more preferably 40to 70 mol %.

The polymeric compound according to the present embodiment is the sameas defined for the component (A1) (polymeric compound including astructural unit (a0)) described above under “(Resist composition)”, andthe kind of each structural unit other than the structural unit (a0),the amount of each structural unit and the like are the same as definedabove for the component (A1).

The polymeric compound of the present embodiment may be produced, forexample, dissolving a monomer which derives a structural unit (a0) (acompound represented by general formula (a0-1)) and, if desired, amonomer which derives a structural unit other than the structural unit(a0) in a polymerization solvent, followed by adding a radicalpolymerization initiator such as azobisisobutyronitrile (AIBN) ordimethyl 2,2′-azobis(isobutyrate) (e.g., V-601) to effect apolymerization reaction. Alternatively, the polymeric compound of thepresent embodiment may be produced by dissolving a monomer which derivesa structural unit (a0) (a compound represented by general formula(a0-1)) and, if desired, a precursor of a monomer which derives astructural unit other than the structural unit (a0) in a polymerizationsolvent, followed by adding a radical polymerization initiator to effecta polymerization reaction, and then conducting a deprotection reaction.

In the polymerization, a chain transfer agent such asHS—CH₂—CH₂—CH₂—C(CF₃)₂—OH may be used to introduce a —C(CF₃)₂—OH groupat the terminal(s) of the polymer. Such a copolymer having introduced ahydroxyalkyl group in which some of the hydrogen atoms of the alkylgroup are substituted with fluorine atoms is effective in reducingdeveloping defects and LER (line edge roughness: unevenness of the sidewalls of a line pattern).

The polymeric compound according to the present embodiment is a novelsubstance useful as a base resin for a resist composition. The polymericcompound may be preferably added to a resist composition as a basecomponent having a film forming ability, and also as a resin component(component (A1)) which exhibits changed solubility in a developingsolution by the action of acid.

(Compound)

The compound of the present embodiment is represented by general formula(a0-1) shown below (hereafter, referred to as “compound (a0)”).

In the formula, W represents a polymerizable group-containing group;Ra⁰¹ represents an alkyl group or an aromatic heterocyclic groupcontaining an oxygen atom or a sulfur atom; in the case where Ra⁰¹ is anaromatic heterocyclic group containing an oxygen atom or a sulfur atom,Ra⁰² is a group which forms an aliphatic cyclic group together with thetertiary carbon atom (*C) to which Ra⁰¹ is bonded, provided that thealiphatic cyclic group contains an electron-withdrawing group as asubstituent; and in the case where Ra⁰¹ is an alkyl group, Ra⁰² is agroup in which an aliphatic cyclic group forms a condensed ring togetherwith an aromatic heterocyclic group containing an oxygen atom or asulfur atom, provided that the aliphatic cyclic group is formed togetherwith the tertiary carbon atom (*C) to which Ra⁰¹ is bonded, and thealiphatic cyclic group contains an electron-withdrawing group as asubstituent.

The compound according to the present embodiment is the same as themonomer which derives the structural unit (a0) described above inrelation to the resist composition of the first aspect.

(Production Method of Compound (a0))

The compound (a0) may be produced by a conventional method. As theproduction method of the compound (a0), for example, a method includingthe following steps (i), (ii) and (iii) may be mentioned.

As the compounds used in each step, commercially available compounds maybe used, or the compounds may be synthesized by a conventional method.

The organic solvent used in each step may be any solvent which iscapable of dissolving compounds used in each step and does not reactwith the compounds. Examples of the organic solvent includedichloromethane, dichloroethane, chloroform, tetrahydrofuran (THF),N,N-dimethylformamide, dimethylacetamide, dimethylsulfoxide,acetonitrile and acetone.

In the formula, W, Ra⁰¹ and Ra⁰² are the same as defined for W, Ra⁰¹ andRa⁰² in the aforementioned formula (a0-1); Ra⁰²′ is the same group asRa⁰² in the aforementioned formula (a0-1), or a group which derives thesame group as Ra⁰²; and X_(ha) represents a halogen atom.

Step (i):

In step (i), for example, a compound (a001) is dissolved in an organicsolvent, followed by dropwise adding a strong base to the solution ofthe compound (a001).

Examples of the strong base include organic alkali metals, such asn-butyllithium, s-butyllithium, t-butyllithium, ethyllithium,ethylsodium, 1,1-diphenylhexyllithium, and1,1-diphenyl-3-methylpentyllithium.

Step (ii):

In step (ii), the solution of the compound (a001) having a strong basedropwise added thereto is mixed with a compound (a002) and a reaction isconducted, so as to obtain an intermediate. The reaction temperature ispreferably −20 to 50° C., more preferably −10 to 40° C. The reactiontime varies, depending on the reactivity of the compound (a001) and thecompound (a002), the reaction temperature, and the like. However, ingeneral, the reaction time is preferably 10 minutes to 12 hours, morepreferably 30 minutes to 6 hours.

Step (iii)

In step (iii), the intermediate obtained in step (ii) is mixed with acompound (a003) and a reaction is conducted, so as to obtain anobjective compound (a0).

X_(ha) represents a halogen atom, and examples thereof include afluorine atom, a chlorine atom, a bromine and an iodine atom, preferablya chlorine atom.

The reaction temperature is preferably −20 to 50° C., more preferably−10 to 40° C. The reaction time varies, depending on the reactivity ofthe intermediate and the compound (a003), the reaction temperature, andthe like. However, in general, the reaction time is preferably 10minutes to 24 hours, more preferably 30 minutes to 12 hours.

After the reaction, the intermediate or the compound (a0) within thereaction mixture may be separated and purified.

The separation and purification can be conducted by a conventionalmethod. For example, any one or more of concentration, solventextraction, distillation, crystallization, re-crystallization andchromatography may be used.

The structure of the compound (a0) obtained in the manner describedabove may be confirmed by a general organic analysis method such as1H-nuclear magnetic resonance (NMR) spectrometry, 13C-NMR spectrometry,19F-NMR spectrometry, infrared absorption (IR) spectrometry, massspectrometry (MS), elementary analysis and X-ray diffraction analysis.

EXAMPLES

As follows is a description of examples of the present invention,although the scope of the present invention is by no way limited bythese examples.

Production Example of Monomer (a01)

59.6 g of thiophene was dissolved in 250 g of THF (tetrahydrofuran), and375 mL of n-butyllithium (1.6 mol/L n-hexane solution) was dropwiseadded to the obtained solution while cooling with ice, followed bystirring for 1 hour. Then, a solution obtained by dissolving 51.6 g oftetrahydrofuran-3-one in 200 g of THF was dropwise added to theresultant, followed by stirring for 1 hour while cooling with ice.Thereafter, a solution obtained by dissolving 56.8 g of methacrylic acidchloride in 400 g of THF was dropwise added to the resulting solution.After further stirring for 1 hour while cooling with ice, 800 g of purewater was dropwise added to the reaction liquid, followed by extractionwith 800 g of heptane. The solvent of the organic phase was removed bydistillation, followed by further purification by distillation, so as toobtain 71.2 g of a monomer (a01) (yield: 55.4%).

The obtained monomer (a01) was analyzed by NMR, and the structurethereof was identified by the following results.

¹H-NMR (DMSO-d6, 400 MHz): δ(ppm)=7.48 (d, thiopene, 1H), 7.12 (d,thiopene, 1H), 6.99 (t, thiopene, 1H), 6.05 (s, C═CH, 1H), 5.70 (m,C═CH, 1H), 4.22-4.26 (d, CH₂O, 1H), 4.03-4.07 (d, CH₂O, 1H), 3.85-3.95(m, CH₂O, 2H), 2.65-2.75 (m, CH, 1H), 2.45-2.55 (m, CH, 1H), 1.85 (s,CH₃, 3H)

Production Example of Monomer (a02)

The same method as in Production Example of monomer (a01) was conducted,except that 51.6 g of tetrahydrofuran-3-one was changed to 60.0 g oftetrahydro-4H-pyran-4-one, so as to obtain 56.5 g of a monomer (a02)(yield: 41.1%).

The obtained monomer (a02) was analyzed by NMR, and the structurethereof was identified by the following results.

¹H-NMR (DMSO-d6, 400 MHz): δ(ppm)=7.49 (d, thiopene, 1H), 7.13 (d,thiopene, 1H), 6.99 (t, thiopene, 1H), 6.03-6.04 (s, C═CH, 1H),5.72-5.73 (m, C═CH, 1H), 3.68-3.72 (m, CH₂O, 4H), 1.88-1.92 (m, CH₂,2H), 1.84-1.86 (s, CH₃, 3H), 1.48-1.51 (m, CH₂, 2H)

Production Example of Monomer (a03)

The same method as in Production Example of monomer (a01) was conducted,except that 59.6 g of thiophene was changed to 69.5 g of2-methylthiophene, so as to obtain 83.9 g of a monomer (a03) (yield:61.0%).

The obtained monomer (a03) was analyzed by NMR, and the structurethereof was identified by the following results.

¹H-NMR (DMSO-d6, 400 MHz): δ(ppm)=6.91 (d, thiopene, 1H), 6.78 (d,thiopene, 1H), 6.05 (s, C═CH, 1H), 5.70 (m, C═CH, 1H), 4.20-4.24 (d,CH₂O, 1H), 4.05-4.08 (d, CH₂O, 1H), 3.85-3.95 (m, CH₂O, 2H), 2.65-2.75(m, CH, 1H), 2.45-2.55 (m, CH, 1H), 2.25 (s, CH₃— Thiophne, 3H), 1.85(s, CH₃, 3H)

Production Example of Monomer (a04)

The same method as in Production Example of monomer (a01) was conducted,except that 59.6 g of thiophene was changed to 48.2 g of furan, so as toobtain 42.1 g of a monomer (a04) (yield: 34.8%).

The obtained monomer (a04) was analyzed by NMR, and the structurethereof was identified by the following results.

¹H-NMR (DMSO-d6, 400 MHz): δ(ppm)=7.591 (d, furan, 1H), 6.43 (d, furan,1H), 6.36 (t, furan, 1H), 6.05 (s, C═CH, 1H), 5.70 (m, C═CH, 1H),4.35-4.38 (d, CH₂O, 1H), 4.15-4.18 (d, CH₂O, 1H), 3.85-3.95 (m, CH₂O,2H), 2.65-2.75 (m, CH, 1H), 2.45-2.55 (m, CH, 1H), 1.85 (s, CH₃, 3H)

Production Example of Monomer (a05)

The same method as in Production Example of monomer (a01) was conducted,except that 51.6 g of tetrahydrofuran-3-one was changed to 60.0 g of2-methyltetrahydrofuran-3-one, so as to obtain 30.9 g of a monomer (a05)(yield: 22.5%).

The obtained monomer (a05) was analyzed by NMR, and the structurethereof was identified by the following results.

¹H-NMR (DMSO-d6, 400 MHz): δ(ppm)=7.49 (d, thiopene, 1H), 7.13 (d,thiopene, 1H), 6.99 (t, thiopene, 1H), 6.03-6.04 (s, C═CH, 1H),5.72-5.73 (m, C═CH, 1H), 4.80-4.84 (m, CH, 1H), 3.76-3.88 (m, CH₂O, 2H),2.40-2.68 (m, CH₂, 2H), 1.84-1.86 (s, CH₃, 3H), 1.48-1.51 (m, CH₂, 2H)

Production Example of Monomer (a06)

30.0 g of thiophene was dissolved in 100 g of THF (tetrahydrofuran), and189 mL of n-butyllithium (1.6 mol/L n-hexane solution) was dropwiseadded to the obtained solution while cooling with ice, followed bystirring for 1 hour. Then, a solution obtained by dissolving 47.1 g of1,4-cyclohexanedione mono(ethylene ketal) in 100 g of THF was dropwiseadded to the resultant, followed by stirring for 1 hour while coolingwith ice. 400 g of pure water was dropwise added to the reaction liquid,followed by extraction with 650 g of heptane. The solvent of the organicphase was removed by distillation, so as to obtain 52.1 g anintermediate-1 (yield: 79.1%).

40.0 g of intermediate-1 was dissolved in 200 g of acetone, and 175 g of1M hydrochloric acid was dropwise added to the obtained solution,followed by stirring at room temperature for 5 hours. Then, 300 g of asaturated aqueous solution of NaHCO₃ was dropwise added to the reactionliquid. Thereafter, extraction was conducted with 300 g of heptane. Thesolvent of the organic phase was removed by distillation, so as toobtain 28.9 g of an intermediate-2 (yield: 88.4%).

25.0 g of intermediate-2, 19.3 g of trimethylamine and 1.56 g ofN,N-dimethyl-4-aminopyridine were dissolved in 250 g of dichloromethane,and a solution obtained by dissolving 16.0 g of methacrylic acidchloride in 32.0 g of dichloromethane was dropwise added to theresulting solution while cooling with ice. Subsequently, the resultantwas stirred at room temperature for 2 hours, and 300 g of pure water wasdropwise added to the reaction liquid, followed by extraction with 300 gof heptane. The solvent of the organic phase was removed bydistillation, followed by further purification by distillation, so as toobtain 24.6 g of a monomer (a06) (yield: 73.2%).

The obtained monomer (a06) was analyzed by NMR, and the structurethereof was identified by the following results.

¹H-NMR (DMSO-d6, 400 MHz): δ(ppm)=7.48 (d, thiopene, 1H), 7.15 (d,thiopene, 1H), 7.01 (t, thiopene, 1H), 6.05 (s, C═CH, 1H), 5.70 (m,C═CH, 1H), 2.86-2.97 (m, CH₂, 2H), 2.14-2.37 (m, CH₂, CH₂O, 6H), 1.85(s, CH₃, 3H)

Production Example of Monomer (a07)

40.0 g of thiophene was dissolved in 150 g of THF (tetrahydrofuran), and251 mL of n-butyllithium (1.6 mol/L n-hexane solution) was dropwiseadded to the obtained solution while cooling with ice, followed bystirring for 1 hour. Then, 46.7 g of a solution obtained by dissolvingtetrahydrothiopyran-4-one in 120 g of THF was dropwise added to theresultant, followed by stirring for 1 hour while cooling with ice. 600 gof pure water was dropwise added to the reaction liquid, followed byextraction with 730 g of heptane. The solvent of the organic phase wasremoved by distillation, so as to obtain 48.6 g of an intermediate-3(yield: 66.4%).

40.0 g of intermediate-3 was dissolved in 400 g of acetone, and 322 g ofan aqueous solution containing 64.4 g of oxone was dropwise added to theresulting solution, followed by stirring at room temperature for 20hours. Then, 460 g of t-butyl methyl ether was added to the reactionliquid to extract the objective substance. The solvent of the organicphase was removed by distillation, so as to obtain 43.6 g of anintermediate-4 (yield: 94.0%).

30.0 g of intermediate-4, 19.6 g of triethylamine and 1.58 g ofN,N-dimethyl-4-aminopyridine was dissolved in 300 g of dichloromethane,and a solution obtained by dissolving 16.2 g of methacrylic acidchloride in 32.4 g of dichloromethane was dropwise added to theresulting solution while cooling with ice. Then, the resultant wasstirred at room temperature for 2 hours, and 400 g of pure water wasdropwise added to the reaction liquid, followed by extraction with 400 gof heptane. The solvent of the organic phase was removed bydistillation, followed by further purification by distillation, so as toobtain 24.7 g of a monomer (a07) (yield: 63.8%).

The obtained monomer (a07) was analyzed by NMR, and the structurethereof was identified by the following results.

¹H-NMR (DMSO-d6, 400 MHz): δ(ppm)=7.48 (d, thiopene, 1H), 7.13 (d,thiopene, 1H), 7.00 (t, thiopene, 1H), 6.05 (s, C═CH, 1H), 5.70 (m,C═CH, 1H), 3.08-3.27 (m, CH₂SO₂, 2H), 2.82-2.95 (m, CH₂SO₂, 2H),1.90-2.50 (m, CH₂, 4H), 1.84-1.86 (s, CH₃, 3H)

Production Example of Copolymer (a1-1-1)

10.0 g of a monomer (a21), 14.8 g of a monomer (a02), 6.9 g of a monomer(a31) and 2.52 g of dimethyl 2,2′-azobis(isobutyrate) (V-601) as apolymerization initiator were dissolved in 48.0 g of MEK (methyl ethylketone) to prepare a dripping solution.

16.8 g of MEK was added to a three-necked flask equipped with athermometer, a reflux tube and a nitrogen-feeding pipe, and then heatedto 85° C. in a nitrogen atmosphere, followed by dropwise adding thedripping solution over 4 hours. After finishing the dropwise addition,the reaction mixture was stirred at the same temperature for 1 hour.Then, the reaction liquid was cooled to room temperature.

Subsequently, the obtained polymer liquid was washed by precipitating in400 g of methanol. The obtained white solid was subjected to filtration,followed by drying under reduced pressure for one night, so as to obtain14.8 g of a polymeric compound (A1-1-1).

With respect to the polymeric compound (A1-1-1), the weight averagemolecular weight (Mw) and the polydispersity (Mw/Mn) were determined bythe polystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 6,900, and the polydispersity was 1.68. Further, asa result of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (150 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was 1/m/n=40/40/20.

Production Example of Copolymer (A1-1-4)

10.0 g of a monomer (a100), 22.0 g of a monomer (a01) and 5.80 g ofdimethyl 2,2′-azobis(isobutyrate) (V-601) as a polymerization initiatorwere dissolved in 64.9 g of MEK (methyl ethyl ketone) to prepare adripping solution. 17.3 g of MEK was added to a three-necked flaskequipped with a thermometer, a reflux tube and a nitrogen-feeding pipe,and then heated to 85° C. in a nitrogen atmosphere, followed by dropwiseadding the dripping solution over 4 hours. After finishing the dropwiseaddition, the reaction mixture was stirred at the same temperature for 1hour. Then, the reaction liquid was cooled to room temperature.Subsequently, 18.4 g of acetic acid and 262 g of methanol were added tothe obtained polymer liquid, and a deprotection reaction was conductedat 30° C. for 8 hours. After the reaction finished, the obtainedreaction liquid was washed by precipitating in 3,900 g of heptane. Theobtained white solid was subjected to filtration, followed by dryingunder reduced pressure for one night, so as to obtain 14.5 g of apolymeric compound (A1-1-4).

With respect to the polymeric compound (A1-1-4), the weight averagemolecular weight (Mw) and the polydispersity (Mw/Mn) were determined bythe polystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 6,600, and the polydispersity was 1.59. Further, asa result of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (150 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was 1/m=40/60.

Production Examples of Other Copolymers

Each of copolymer (A1-1-2), copolymer (A1-1-9), copolymers (A2-1) to(A2-4) and copolymer (A2-8) was synthesized in substantially the samemanner as in the above <Production example of copolymer (A1-1-1)>,except that monomers for deriving the structural units that constituteeach copolymer were used in a predetermined molar ratio.

Each of copolymer (A1-1-3), copolymers (A1-1-5) to (A1-1-8), andcopolymers (A2-5) to (A2-7) was synthesized in substantially the samemanner as in the above <Production example of copolymer (A1-1-4)>,except that monomers for deriving the structural units that constituteeach copolymer were used in a predetermined molar ratio.

Copolymers (A1-1-1) to (A1-1-9) and copolymers (A2-1) to (A2-8) obtainedin the above production examples are shown below.

With respect to each copolymer, the compositional ratio of the polymers(the molar ratio of the respective structural units in the polymericcompound) as determined by ¹³C-NMR, the weight average molecular weight(Mw) and the polydispersity (Mw/Mn) determined by the polystyreneequivalent value as measured by GPC are also shown in Table 1.

TABLE 1 Weight average Amount of structural molecular unit derived fromweight Polydispersity Copolymer each monomer (molar ratio) (Mw) (Mw/Mn)(A1-1-1) (a21)/(a02)/(a31) = 40/40/20 6900 1.68 (A1-1-2) (a21)/(a02) =40/60 6100 1.65 (A1-1-3) (a101)/(a07) = 40/60 7500 1.61 (A1-1-4)(a101)/(a01) = 40/60 6600 1.59 (A1-1-5) (a101)/(a03) = 40/60 7700 1.62(A1-1-6) (a101)/(a04) = 40/60 7300 1.55 (A1-1-7) (a101)/(a06) = 40/607700 1.55 (A1-1-8) (a101)/(a05) = 40/60 8000 1.54 (A1-1-9) (a102)/(a02)= 30/70 6600 1.60 (A2-1) (a21)/(a11)/(a31) = 40/40/20 7800 1.80 (A2-2)(a21)/(a12)/(a31) = 40/40/20 7000 1.66 (A2-3) (a21)/(a11) = 40/60 67001.70 (A2-4) (a21)/(a13) = 40/60 6000 1.65 (A2-5) (a101)/(a11) = 40/606200 1.55 (A2-6) (a101)/(a14) = 40/60 6600 1.53 (A2-7) (a101)/(a15) =40/60 7300 1.63 (A2-8) (a102)/(a11) = 30/70 6900 1.62

Production of Resist Composition Examples 1 to 9, Comparative Examples 1to 8

The components shown in Table 2 were mixed together and dissolved toobtain each resist composition (solid content: 3.0 wt %).

TABLE 2 Component Component Component (A) (B) (D) Component (S) Example1 (A)-1 (B)-1 (D)-1 (S)-1 (S)-2 [100] [21.6] [3.1] [4800] [3200] Com-(A)-2 (B)-1 (D)-1 (S)-1 (S)-2 parative [100] [21.6] [3.1] [4800] [3200]Example 1 Com- (A)-3 (B)-1 (D)-1 (S)-1 (S)-2 parative [100] [21.6] [3.1][4800] [3200] Example 2 Example 2 (A)-4 (B)-1 (D)-1 (S)-1 (S)-2 [100][21.6] [3.1] [4800] [3200] Com- (A)-5 (B)-1 (D)-1 (S)-1 (S)-2 parative[100] [21.6] [3.1] [4800] [3200] Example 3 Com- (A)-6 (B)-1 (D)-1 (S)-1(S)-2 parative [100] [21.6] [3.1] [4800] [3200] Example 4 Example 3(A)-7 (B)-1 (D)-1 (S)-1 (S)-2 [100] [21.6] [3.1] [4800] [3200] Example 4(A)-8 (B)-1 (D)-1 (S)-1 (S)-2 [100] [21.6] [3.1] [4800] [3200] Example 5(A)-9 (B)-1 (D)-1 (S)-1 (S)-2 [100] [21.6] [3.1] [4800] [3200] Example 6(A)-10 (B)-1 (D)-1 (S)-1 (S)-2 [100] [21.6] [3.1] [4800] [3200] Example7 (A)-11 (B)-1 (D)-1 (S)-1 (S)-2 [100] [21.6] [3.1] [4800] [3200]Example 8 (A)-12 (B)-1 (D)-1 (S)-1 (S)-2 [100] [21.6] [3.1] [4800][3200] Com- (A)-13 (B)-1 (D)-1 (S)-1 (S)-2 parative [100] [21.6] [3.1][4800] [3200] Example 5 Com- (A)-14 (B)-1 (D)-1 (S)-1 (S)-2 parative[100] [21.6] [3.1] [4800] [3200] Example 6 Com- (A)-15 (B)-1 (D)-1 (S)-1(S)-2 parative [100] [21.6] [3.1] [4800] [3200] Example 7 Example 9(A)-16 (B)-1 (D)-1 (S)-1 (S)-2 [100] [21.6] [3.1] [4800] [3200] Com-(A)-17 (B)-1 (D)-1 (S)-1 (S)-2 parative [100] [21.6] [3.1] [4800] [3200]Example 8

In Table 2, the reference characters indicate the following. The valuesin brackets [ ] indicate the amount (in terms of parts by weight) of thecomponent added.

(A)-1: The above copolymer (A1-1-1)

(A)-2: The above copolymer (A2-1)

(A)-3: The above copolymer (A2-2)

(A)-4: The above copolymer (A1-1-2)

(A)-5: The above copolymer (A2-3)

(A)-6: The above copolymer (A2-4)

(A)-7 to (A)-12: The above copolymers (A1-1-3) to (A1-1-8)

(A)-13 to (A)-15: The above copolymers (A2-5) to (A2-7)

(A)-16: The above copolymer (A1-1-9)

(A)-17: The above copolymer (A2-8)

(B)-1: an acid generator consisting of a compound represented bychemical formula (B)-1 shown below

(D)-1: acid diffusion control agent of a compound represented bychemical formula (D)-1 below

(S)-1: propyleneglycol monomethyletheracetate

(S)-2: propylene glycol monomethyl ether

<Formation of Resist Pattern>

Each of the resist compositions of examples and comparative examples wasapplied to an 8-inch silicon substrate which had been treated withhexamethyldisilazane (HMDS) using a spinner, and was then prebaked (PAB)on a hot plate at 110° C. for 60 seconds and dried, thereby forming aresist film having a film thickness of 30 nm.

Subsequently, the resist film was subjected to drawing (exposure) usingan electron beam lithography apparatus JEOL JBX-9300FS (manufactured byJEOL Ltd.) at an acceleration voltage of 100 kV, targeting a 1:1 lineand space pattern (hereafter, referred to as “L/S pattern”) having lineswith a width of 50. Then, a post exposure bake (PEB) treatment wasconducted at 110° C. for 60 seconds.

Thereafter, alkali developing was conducted for 60 seconds at 23° C. ina 2.38% by weight aqueous solution of tetramethylammonium hydroxide(TMAH) (product name: NMD-3; manufactured by Tokyo Ohka Kogyo Co.,Ltd.). Then, water rinsing was conducted for 15 seconds using purewater.

As a result, a 1:1 line and space pattern (LS pattern) having a linewidth of 50 nm was formed.

[Evaluation of Optimum Exposure Dose (Eop)]

The optimum exposure dose Eop (C/cm²) with which the LS pattern wasformed in the above formation of resist pattern was determined. Theresults are indicated under “Eop (C/cm²)” in Table 3.

[Evaluation of Line Width Roughness (LWR)]

With respect to a resist pattern formed by the above method of“Formation of resist pattern”, 30 was determined as a yardstick forindicating LWR. The results are indicated under “LWR (nm)” in Table 3.

“3σ” indicates a value of 3 times the standard deviation (σ) (i.e., 3σ)(unit: nm) determined by measuring the line positions at 400 points inthe lengthwise direction of the line using a scanning electronmicroscope (product name: S-9380, manufactured by HitachiHigh-Technologies Corporation; acceleration voltage: 800V).

The smaller this 30 value is, the lower the level of roughness on theside walls of the line, indicating that an L/S pattern with a uniformwidth was obtained.

[Evaluation of Resolution]

The critical resolution (nm) with the above Eop was determined using ascanning electron microscope (product name: S-9380, manufactured byHitachi High-Technologies Corporation). Specifically, the exposure dosewas gradually increased from the optimum exposure dose Eop, and theminimum size of the pattern which resolves without collapse (fall) wasdetermined. The results are indicated under “Critical resolution (nm)”in Table 3.

[Evaluation of Size (Dimension) with Lapse of Time]

Using resist composition of each example which had been stored at roomtemperature for 1 month, a 1:1 L/S pattern targeting a line width of 50nm was formed by the above method of “Formation of resist pattern”. Fromthe measured pattern size of an US pattern formed using a resistcomposition before the storing, the amount of change in the pattern sizewas determined, and the change in the size with lapse of time wasevaluated in accordance with the following criteria. The results areindicated under “Size with lapse of time” in Table 3.

(Criteria)

A: Amount of change in size was 1 nm or less

B: Amount of change in size was more than 1 nm

TABLE 3 Size Critical with PAB PEB Eop LWR resolution lapse of (° C.) (°C.) (μC/cm²) (nm) (nm) time Example 1 110 110 101 6.1 28 A Comparative110 110 127 6.7 40 A Example 1 Comparative 110 110 154 7.5 50 A Example2 Example 2 110 110 79 5.8 26 A Comparative 110 110 122 6.6 40 A Example3 Comparative 110 110 49 8.3 50 B Example 4 Example 3 110 110 60 5.5 26A Example 4 110 110 54 5.0 24 A Example 5 110 110 61 5.0 26 A Example 6110 110 55 5.4 24 A Example 7 110 110 67 5.5 26 A Example 8 110 110 535.3 26 A Comparative 110 110 88 6.4 32 A Example 5 Comparative 110 11037 8.8 50 B Example 6 Comparative 110 110 109 7.0 36 A Example 7 Example9 110 110 52 5.8 26 A Comparative 110 110 81 7.4 36 A Example 8

As seen from the results shown in Table 3, from comparison betweenExample 1 and Comparative Examples 1 and 2, comparison between Example 2and Comparative Examples 3 and 4, comparison between Examples 3 to 8 andComparative Examples 5 and 6, and comparison between Examples 9 andComparative Examples 7 and 8, according to the resist composition of theexamples which applied the present invention, high sensitivity can beachieved in the formation of a resist pattern, and a resist patternexhibiting excellent lithography properties (resolution, reducedroughness) can be formed, as compared to the comparative examples.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

What is claimed is:
 1. A resist composition which generates acid uponexposure and exhibits changed solubility in a developing solution underaction of acid, wherein the resist composition comprises a resincomponent (A1) which exhibits changed solubility in a developingsolution under action of acid, and the resin component (A1) comprises astructural unit (a0) derived from a compound represented by generalformula (a0-1) shown below:

wherein W represents a polymerizable group-containing group; Ra⁰¹represents an alkyl group or an aromatic heterocyclic group containingan oxygen atom or a sulfur atom; in the case where Ra⁰¹ is an aromaticheterocyclic group containing an oxygen atom or a sulfur atom, Ra⁰² is agroup which forms an aliphatic cyclic group together with the tertiarycarbon atom (*C) to which Ra⁰¹ is bonded, provided that the aliphaticcyclic group contains an electron-withdrawing group as a substituent;and in the case where Ra⁰¹ is an alkyl group, Ra⁰² is a group in whichan aliphatic cyclic group forms a condensed ring together with anaromatic heterocyclic group wherein the aromatic heterocyclic groupcontains an oxygen atom or a sulfur atom, provided that the aliphaticcyclic group is formed together with the tertiary carbon atom (*C) towhich Ra⁰¹ is bonded, and the aliphatic cyclic group contains anelectron-withdrawing group as a substituent.
 2. The resist compositionaccording to claim 1, wherein in general formula (a0-1), Ra⁰¹ representsan aromatic heterocyclic group containing an oxygen atom or a sulfuratom, and Ra⁰² is a group which forms a group represented by any one offormulae (Ra⁰²-1) to (Ra⁰²-17) shown below together with the tertiarycarbon atom (*C) to which Ra⁰¹ is bonded:

wherein *1 indicates a valence bond which is bonded to W—C(═O)O—; and *2indicates a valence bond which is bonded to Ra⁰¹.
 3. The resistcomposition according to claim 2, wherein Ra⁰¹ is a group represented byany one of formulae (Ra⁰¹-1) to (Ra⁰¹-8) shown below:

wherein * indicates a valence bond which is bonded to the tertiarycarbon atom (*C).
 4. The resist composition according to claim 1,wherein in general formula (a0-1), Ra⁰¹—(C*)(Ra⁰²) is a condensed ringrepresented by any one of formulae (Ra⁰²-21) to (Ra⁰²-24) shown below:

wherein *1 indicates a valence bond which is bonded to W—C(═O)O—.
 5. Amethod of forming a resist pattern, comprising: forming a resistcomposition using the resist film according to claim 1; exposing theresist film; and developing the exposed resist film to form a resistpattern.
 6. A polymeric compound comprising a structural unit (a0)derived from a compound represented by general formula (a0-1) shownbelow:

wherein W represents a polymerizable group-containing group; Ra⁰¹represents an alkyl group or an aromatic heterocyclic group containingan oxygen atom or a sulfur atom; in the case where Ra⁰¹ is an aromaticheterocyclic group containing an oxygen atom or a sulfur atom, Ra⁰² is agroup which forms an aliphatic cyclic group together with the tertiarycarbon atom (*C) to which Ra⁰¹ is bonded, provided that the aliphaticcyclic group contains an electron-withdrawing group as a substituent;and in the case where Ra⁰¹ is an alkyl group, Ra⁰² is a group in whichan aliphatic cyclic group forms a condensed ring together with anaromatic heterocyclic group, wherein the aromatic heterocyclic groupcontains an oxygen atom or a sulfur atom, provided that the aliphaticcyclic group is formed together with the tertiary carbon atom (*C) towhich Ra⁰¹ is bonded, and the aliphatic cyclic group contains anelectron-withdrawing group as a substituent.
 7. The polymeric compoundaccording to claim 6, wherein in general formula (a0-1), Ra⁰¹ representsan aromatic heterocyclic group containing an oxygen atom or a sulfuratom, and Ra⁰² is a group which forms a group represented by any one offormulae (Ra⁰²-1) to (Ra⁰²-17) shown below together with the tertiarycarbon atom (*C) to which Ra⁰¹ is bonded:

wherein *1 indicates a valence bond which is bonded to W—C(═O)O—; and *2indicates a valence bond which is bonded to Ra⁰¹.
 8. The polymericcompound according to claim 7, wherein Ra⁰¹ is a group represented byany one of formulae (Ra⁰¹-1) to (Ra⁰¹-8) shown below:

wherein * indicates a valence bond which is bonded to the tertiarycarbon atom (*C).
 9. The polymeric compound according to claim 6,wherein in general formula (a0-1), Ra⁰¹—(C*)(Ra⁰²) is a condensed ringrepresented by any one of formulae (Ra⁰²-21) to (Ra⁰²-24) shown below:

wherein *1 indicates a valence bond which is bonded to W—C(═O)O—.
 10. Acompound represented by general formula (a0-1) shown below:

wherein W represents a polymerizable group-containing group; Ra⁰¹represents an alkyl group or an aromatic heterocyclic group containingan oxygen atom or a sulfur atom; in the case where Ra⁰¹ is an aromaticheterocyclic group containing an oxygen atom or a sulfur atom, Ra⁰² is agroup which forms an aliphatic cyclic group together with the tertiarycarbon atom (*C) to which Ra⁰¹ is bonded, provided that the aliphaticcyclic group contains an electron-withdrawing group as a substituent;and in the case where Ra⁰¹ is an alkyl group, Ra⁰² is a group in whichan aliphatic cyclic group forms a condensed ring together with anaromatic heterocyclic group wherein the aromatic heterocyclic groupcontains an oxygen atom or a sulfur atom, provided that the aliphaticcyclic group is formed together with the tertiary carbon atom (*C) towhich Ra⁰¹ is bonded, and the aliphatic cyclic group contains anelectron-withdrawing group as a substituent.
 11. The compound accordingto claim 10, wherein in general formula (a0-1), Ra⁰¹ represents anaromatic heterocyclic group containing an oxygen atom or a sulfur atom,and Ra⁰² is a group which forms a group represented by any one offormulae (Ra⁰²-1) to (Ra⁰²-17) shown below together with the tertiarycarbon atom (*C) to which Ra⁰¹ is bonded:

wherein *1 indicates a valence bond which is bonded to W—C(═O)O—; and *2indicates a valence bond which is bonded to Ra⁰¹.
 12. The compoundaccording to claim 11, wherein Ra⁰¹ is a group represented by any one offormulae (Ra⁰¹-1) to (Ra⁰¹-8) shown below:

wherein * indicates a valence bond which is bonded to the tertiarycarbon atom (*C).
 13. The compound according to claim 10, wherein ingeneral formula (a0-1), Ra⁰¹—(C*)(Ra⁰²) is a condensed ring representedby any one of formulae

wherein *1 indicates a valence bond which is bonded to W—C(═O)O—.